Short-range cellular booster

ABSTRACT

A repeater mediates traffic between a network transceiver and a user transceiver in a wireless communication system. The repeater comprises a network unit that maintains a network link with the network transceiver, a user unit that maintains a user link with the user transceiver, a two-way communication pathway between the network unit and the user unit; that facilitate the communication of signals between the network transceiver and the user transceiver in autonomous repeater hops between the network transceiver and the network unit, between the user transceiver and the user unit, and between the network unit and the user unit, and beam-formers respectively coupled to the network unit and the user unit and adapted to communicate signals in an operating frequency band of the network and user transceivers and to control effective radiated power.

BACKGROUND

The existing cellular networks, such as (Global System for MobileCommunications (GSM) and IS95, are intended to provide a contagious andcontinuous coverage, so as to support the high terminal mobilityexpected from such systems. However, despite careful network design,indoor (in-building) coverage, or the coverage of places with highshadowing attenuation (e.g. tunnels) of such networks is often “patchy”,with “coverage Holes” at best, and no coverage at worst. The reason forthe impaired indoor coverage is that the cellular base stations areusually placed outside buildings, higher than the average buildingheights, to provide large area coverage. Although the signal may beadequate at “street-level”, it is severely attenuated by the buildingmaterial, reducing the signal power in-building, resulting in the poorconverges. Loss of signal power (attenuation) depends on the buildingmaterial and can be tens of dBs for each wall penetration. The problemis exacerbated in the 3^(rd) generation systems such as Wideband CodeDivision Multiple Access (WCDMA) and cdma2000, as these new systems havethe capability of high data transmission, which results in lowerinformation bit energy (E_(b)), and much reduced link budget and cellfoot-print. Currently, the common solutions for providing indoorcoverage are:

-   -   I) More outdoor base stations in the same geographical area,        supporting smaller cell sizes.    -   II) Microcells.    -   III) Picocells (in-building cells).    -   IV) Conventional repeaters.

Clearly all the above solutions (except the repeater solution) are veryexpensive and involve extensive investment in the cellular networkinfrastructure and are much more complex in planning and operation.There are other solutions such as repeaters that can be used to boostthe signal in a given geographical area.

The repeater solution, although cheaper than a base station, has severaldrawbacks. These outdoor repeaters are still too expensive for a privateuser, and involve careful planning. Most use large directional antennas,or additional backhaul frequencies to reduce antenna gainspecifications, which results in lower spectral efficiency and arecapacity limited. The repeaters tend to transmit the maximum allowedtransmit power and often cause increased interference in the network andaccordingly may be unsuitable for network operators. The indoorrepeaters are still cheaper than the outdoor version, but typicallyinvolve installation of high directional antennas on the roof, andensured antenna isolation, creating costly demand for skilledinstallation and operation. Therefore, the system generally remains toocomplicated for an unskilled user and not sufficiently inexpensive forusage in a much localized coverage area.

SUMMARY

In accordance with an embodiment of a communication device, a repeatermediates traffic between a network transceiver and a user transceiver ina wireless communication system. The repeater comprises a network unitthat maintains a network link with the network transceiver, a user unitthat maintains a user link with the user transceiver, a two-waycommunication pathway between the network unit and the user unit; thatfacilitate the communication of signals between the network transceiverand the user transceiver in autonomous repeater hops between the networktransceiver and the network unit, between the user transceiver and theuser unit, and between the network unit and the user unit, and abeam-formers respectively coupled to the network unit and the user unitand adapted to communicate signals in an operating frequency band of thenetwork and user transceivers and to control effective radiated power.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention relating to both structure and method ofoperation may best be understood by referring to the followingdescription and accompanying drawings whereby:

FIG. 1 is a schematic block diagram illustrating an embodiment of acellular network with two base stations;

FIG. 2 is a schematic block diagram depicting an embodiment of aforward-link part of a repeater;

FIG. 3 is a schematic block diagram showing an embodiment of areverse4ink part of a repeater;

FIG. 4 is a schematic block diagram illustrating an embodiment of asystem including a Network unit and a User unit;

FIG. 5 is a schematic block diagram that illustrates an embodiment of asystem including a Network unit implementing antenna diversity;

FIG. 6 is a schematic block diagram depicting an embodiment of arepeater that uses two antennas for antenna diversity;

FIGS. 7A, 7B, 7C, and 7D are flow charts depicting embodiments of systemoperation flow for a network unit;

FIGS. 8A, 8B, 8C, and 8D are flow charts depicting embodiments of systemoperation flow for a user unit;

FIG. 9 is a schematic block diagram illustrating an embodiment of adigital implementation of a network unit including multiple antennaswhich may be used for antenna diversity;

FIG. 10 is a schematic block diagram illustrating an embodiment of adigital implementation of a user unit including multiple antennas whichmay be used for antenna diversity;

FIG. 11 is a schematic block diagram showing an embodiment of an analogimplementation of a back-to-back repeater;

FIG. 12 is a schematic block diagram showing an embodiment of a digitalimplementation of a back-to-back repeater;

FIGS. 13A, 13B, and 13C are flow charts showing an embodiment ofoperation flow of a back-to-back repeater;

FIGS. 14A and 14B are a simplified block diagram and a spectral graphwhich illustrate a channel filtering operation;

FIGS. 15A, 15B, and 15C respectively illustrate a block diagram of achannel filter, a spectral plot showing channel filter coefficients, anda table depicting the coefficients for an embodiment of a channelfilter; and

FIGS. 16-19 are schematic block diagrams showing other repeaterembodiments.

DETAILED DESCRIPTION

The system disclosed herein provides better, and localized indoorcoverage without causing excess interference in the network, usage ofcostly equipment or network planning. The system increases the overallnetwork capacity, reducing the mobile and BTS transmit power, increasingthe battery life and reducing the “harmful” radiation to the user.

Descriptions of the illustrated embodiments are based on a GSM (GlobalSystem for Communications) network, which is a Time Division MultipleAccess-Frequency Division Duplex (TDMA/FDD) based system operating atvarious spectrum bands, depending on the country and the region'sregulations. However, the disclosure, with minor modifications, isequally applicable to any other cellular system, including (but notlimited to) IS95, cdma2000 and WCDMA, and with further modificationsapplicable to wireless LAN systems such as 802.11a, b, and g. Althoughthe description is given for cellular systems, with minor modifications,it can equally be applied to other systems such as GPS or any othersystem that uses signal-boosting capability. The operating frequency canbe at a selected part of communications spectrum used for mobilecommunications (e.g. PCS 1900, or DCS1800 or GSM900 or UMTS 2000, ISM orUNII band). The description here is only intended as an example and assuch utilization of the booster is not only limited to the in-buildingcoverage and can be used in other places such as trains, planes, cars,tunnels, etc. Also, the example may not include all minute orunimportant design details. Units and sub-units discussed and explainedhereafter meet regulations of the respective licensed and unlicensedband of operation. Therefore, for the different example implementationsand embodiments disclosed, specifications including maximum transmitpower, spectral mask, out of band radiation, and others fortransmitters, receivers, repeaters and boosters, are met for bothlicensed and unlicensed bands of operation.

Analogue Implementation Example

FIG. 1 shows a cellular network 100 with two base stations (BTS1 (101) &BTS2 (102)). A typical network supports more than two base stations. Thedisclosed system may be applied in any size network, regardless of thesupported number of base stations. BTS1 101 is connected to Base StationController BSC1 107. BTS2 102 is connected to Base Station ControllerBSC2 108. BTS2 102 can also be connected to Base Station Controller BSC1107, instead of BSC2 108. BSC1 107 is connected to Mobile SwitchingCenter MSC 109. BSC2 108 is connected to MSC 109, or instead may beconnected to another MSC in the network. MSC 109 is connected to PSTN110. BTS1 101 has an associated coverage area 103. BTS2 102 has anassociated coverage area 104. These coverage areas may or may notoverlap. However, usually the network is planned such that there isconsiderable overlap, to facilitate handoffs. The mobile terminal 105 isinside building 106, in the coverage area 103 communicating with BTS1101, using a traffic channel transmitted at around frequency f1 in theforward-link and its associated reverse-link frequency, f1′. The trafficchannel can be one of the available time slots on the BCCH carrier, ormay be on a TCH carrier, where frequency hopping may be used to reduceinterference. Mobile terminal 105 may or may not be in coverage area104, but the mobile unit 105 is well within the coverage area 103 andaverage signal power from BTS1 101 is much stronger than the averagesignal power from BTS2 102, within the building 106, and the locality ofmobile unit 105. Root-mean-square (rms) forward-link signal level Ŝ₁,outside the building 106 is higher than the rms signal level Ŝ₂ insidethe building by the wall penetration loss α. The loss α may be such thatŜ₂ is not at sufficiently high level for the mobile unit 105 to maintainreliable communication with BTS1 101, or BTS2 102, or both BTS1 101 andBTS2 102. Further, the signal level Ŝ₂ may be such that mobile unit 105may have difficulty to setup and maintain a communication link with BTS1101 or BTS2 102, or both BTS1 101 and BTS2 102, or the communicationlink does not have the selected performance and reliability, in all orsome of the in-building areas. The coverage problem inside the building106 may be solved by more transmit power from BTS1 101 in the down-linkto combat the signal loss, by the wall penetration loss, α. The rmsreverse-link signal level Ŝ′₁, inside the building 106 is higher thanthe rms signal level Ŝ′₂, outside the building, by the wall penetrationloss α′. The loss α′ may be such that Ŝ′₂ is not at sufficiently highlevel for the mobile unit 105 to maintain reliable communication withBTS1 101, or BTS2 102, or both BTS1 101 and BTS2 102. Further, thesignal level Ŝ′₂ may be such that mobile unit 105 may have difficulty tosetup and maintain a communication link with BTS1 101 or BTS2 102, orboth BTS1 101 and BTS2 102, or the communication link does not have theselected performance and reliability, in all or some of the in-buildingareas. The coverage problem inside the building 106 may be solved bymore transmit power from mobile unit 105 in the up-link to combat thesignal loss, by the wall penetration loss, α′. Usually the forward andreverse link frequency pairs are sufficiently close, such that α levelis substantially similar to α′ level.

FIG. 2 depicts a forward-link part 230 of the repeater 200. Theforward-link portion 230 in a simple form supplies improved indoorcoverage by boosting the signal level in building in the forward-link ofthe cellular network. BTS1 213 has a BCCH radio channel (beacon channel)transmitted substantially close to f1. BTS1 213 is in communicationswith the mobile unit 214 at a frequency substantially close to f1 (theBCCH carrier frequency) or another carrier frequency, f2, that may ormay not be frequency hopping. There may or may not be other frequenciesthat are transmitted by BTS1 213, or other base stations in the samearea, which are not shown in the FIG. 2.

The device has two separate units, the “Forward-link Network unit” 201,which is placed where good signal coverage exists, indoor or outdoors,and the “Forward-link User unit” 202, which is placed where good signalcoverage does not exist, indoor or outdoors. The Forward-link Networkunit 201 is connected to an antenna 203, tuned to operate at thecellular network operating frequency band. The Forward-link Network unit201 is also connected to an antenna 204 tuned to operate at suitableUnlicensed National Information Infrastructure (known as U-NII) bands,where the system is designed to operate at U-NII spectrum bands. Subjectto the relevant regulations, the system can also be designed to operateat Unlicensed Personal Communications Services (U-PCS) band or atIndustrial, Scientific and Medical (ISM) band of frequencies. The choiceof the unlicensed frequency depends on the design of the equipment andthe system specification. Frequencies defined in the portion of theradio spectrum known as U-NII bands may be implemented in someembodiments. Some design modifications are useful, for ISM bandoperation. The modifications are related to the minimum spreading factorof 10 specified for the ISM band operation, and the maximum allowedtransmit power. If the system is designed to operate in ISM band, thesignal may use further spread spectrum modulation/demodulation and othermodifications to meet FCC 47 CFR Part-15, subpart E specifications.

The frequency bands defined for U-NII operations are as follows:

1) 5.15-5.25 GHz @ Max Transmit power of 2.5 mW/MHz

2) 5.25-5.35 GHz @ Max Transmit power of 12.5 mW/MHz

3) 5.725-5.825 GHz @ Max Transmit power of 50 mW/MHz

Any unlicensed operation in U-NII band is allowed, as long as the signaltransmissions meet FCC 47 CFR Part-15. So operation of the describedbooster generally complies with standards of the FCC 47 CFR Part-15(subpart E for U-NII frequencies). Regulations commonly specify transmitpower, emission limits, and the antenna gain limits and are implementedfor an acceptable device.

The “Forward-link User Unit” 202 is connected to an antenna 205 tuned tooperate in the same frequency band as antenna 204, which is U-NII bandin some embodiments. The Forward-link User unit 202 is also connected toan antenna 206 tuned to operate at the cellular network operating band.

Antenna 203 is connected to a (Low Noise Amplifier) LNA unit 207, whichis further connected to a bandpass filter 232. LNA unit 207 may be ahigh performance amplifier, with a typical gain of 15 dB and a noisefigure of 1.5 dB with sufficient bandwidth to cover the appropriateportion of the spectrum manually or automatically. The bandpass filter232 can be designed to pass all or a desired part of the interestedcellular spectrum, or can be a bank of overlapping bandpass filters,covering the full spectrum of the interested cellular system, with a RFswitch, such that the selected band and bandwidth can be selected. Thebandpass filter 232 is connected to frequency converter 208. Thefrequency converter 208 is capable of converting the cellular networkoperating spectrum band to a desirable part of the U-NII spectrum, andincludes components such as mixers and filters for correct operation.The frequency converter 208 is connected to the Forward-link Networkunit transmitter 209. The transmitter unit 209 is designed to operate inU-NII band and conforms to the FCC 47 CFR Part-15, subpart Eregulations, and can be as simple as a single amplifier operating at thedesirable U-NII operation band, or more complex transmitter withamplifiers and filters, or even a WLAN transmitter such as 802.11a. Thetransmitter unit 209 is connected to antenna 204.

Antenna 205 is connected to the Forward-link User unit receiver 210,which is designed to receive the signal transmitted by unit 201. Thereceiver 210 which is connected to frequency converter 211, can be assimple as a single LNA operating at desirable U-NII band of deviceoperation, or it can be better designed with additional functionalitiessuch as automatic gain control (AGC), multiple cascaded amplificationstages, and variable channel select filters, or even a Wireless LocalArea Network (WLAN) receiver such as 802.11a (where the transmitter partof 802.11a is used in the Network unit 209). If automated gain control(AGC) is used in receiver 210 and the unit is designed for Code DivisionMultiple Access (CDMA) cellular networks, performance is enhanced byselecting AGC bandwidth to be substantially smaller than the powercontrol repetition rate of the CDMA system, for example less than 1.5kHz in WCDMA networks, so that AGC operation does not interfere withclosed-loop power control. Frequency converter unit 211, which isconnected to receiver unit 210 and variable gain amplifier unit 212,converts the input signals, from U-NII band, to the cellular networkoperating frequencies, and includes all components such as mixers andfilters for correct operation. The frequency converter unit 211 performsthe opposite conversion operation of the frequency converter unit 208,and includes all components such as mixers and filters for correctoperation. The frequency converter 211 is connected to the Variable Gain(VG) amplifier 212, operating at the cellular network operatingfrequency band. The variable gain amplifier 212 is connected to antenna206, which transmits signals with substantially similar frequencies tothe frequencies transmitted by base station 213 and conforms to cellularsystem specifications.

The signal radiated by antenna 208, which is an amplified repeatedversion of the original incident signal received by antenna unit 203,will experience some loss in the power level, before returning andre-entering the antenna 203 again. The re-entered signal into antenna203 is termed “Down-link Returned-Signal” hereafter. The ratio of therms signal value of the Down-link Returned-Signal to the rms value ofthe original incident signal at the output of the antenna 203terminator, with system and propagation path delays between the antennaunits 208 and 203 removed, is the Down-link Returned-Signal path loss,and is termed here as the “Down-link System Path Loss” and referred toas PL_(dl).

Further, the “Down-link System Link Gain”, which is here referred to asG_(dl), is defined as “the ratio of the rms signal value at the input tothe antenna 208 terminator, to the rms signal value, at the antenna 203terminator, where the Down-link System Path Loss, PL_(dl), as definedabove, is infinite (for example no EM coupling path between antenna 208and antenna 203), and all the system and propagation path delays (fromantenna 203, through the system to antenna 208) are removed”.

The variable gain amplifier unit 212 gain is set such that Down-linkSystem Link Gain, G_(dl), is less than the Down-link System Path Loss,PL_(dl), by dg_(dl), so as to avoid a “positive feed-back” loop in thesystem, for example,

G _(dl=) PL _(dl) −dg _(dl) (dB)

Note that all values of PL_(dl), G_(dl), and dg_(dl) are all in dB. Thevalue of dg_(dl) ranges from 0 to PL_(dl), and can be assumed to be 3 dBfor the purposes of the description here. However, it is possible toselect better values for dg_(dl), where the system performance isoptimized further.

FIG. 3 depicts an embodiment of the reverse-link part 330 of a repeater300. The reverse-link portion 330 in a simple form improves indoorcoverage by boosting signal level in building in the reverse-link of thecellular network to such level that attains acceptable link performance.BTS1 302 has a BCCH radio channel (beacon channel) transmittedsubstantially close to f1, and a frequency pair, f′1 on thereverse-link. BTS1 302 is in communications with the mobile unit 324 ata frequency substantially close to f′1 (the BCCH carrier frequency) oranother carrier frequency, f′2, that may or may not be frequencyhopping. There may or may not be other frequencies that are transmittedby BTS1 302, or other base stations in the same area, which are notshown in the FIG. 3.

The device has two separate units, the “Reverse-link Network unit” 326,which is placed where good signal coverage exists, indoor or outdoors,and the “Reverse-link User unit” 328, which is placed where good signalcoverage does not exist, indoor or outdoors. The Reverse-link Networkunit 326 is connected to an antenna 304, tuned to operate at thecellular network operating frequency band. The Reverse-link Network unit326 is also connected to an antenna 312 tuned to operate at suitableUnlicensed National Information Infrastructure (J-NII) bands, where thesystem is designed to operate at U-NII bands. Subject to the relevantregulations, the system can also be designed to operate at UnlicensedPersonal Communications Services (J-PCS) band or at Industrial,Scientific and Medical (ISM) band of frequencies. The choice of theunlicensed frequency depends on the design of the equipment and thesystem specification. Frequencies defined in the portion of the radiospectrum known as U-NII bands may be used in some system designs. Somedesign modifications are used for ISM band operation. The modificationsare related to the minimum spreading factor of 10 used for ISM bandoperation, and the maximum allowed transmit power. If the system isdesigned to operate in ISM band, the signal uses further spread spectrummodulation/demodulation and other modifications to meet the FCC 47 CFRPart-15, subpart E specifications.

The frequency bands defined for U-NII operations are as follows:

1) 5.15-5.25 GHz @ Max Transmit power of 2.5 mW/MHz

2) 5.25-5.35 GHz @ Max Transmit power of 12.5 mW/MHz

3) 5.725-5.825 GHz @ Max Transmit power of 50 mW/MHz

Any unlicensed operation in U-NII bands is allowed, as long as thesignal transmissions meet with FCC 47 CFR Part-15. Operation of theillustrative booster meets specifications of FCC 47 CFR Part-15 (subpartE for U-NII frequencies).

The “Reverse-link User Unit” 328 is connected to an antenna 314 tuned tooperate in the same frequency band as antenna 312, which is U-NII bandfor example. The Reverse-link User unit 328 is also connected to anantenna 322 tuned to operate at cellular network operating band.

Antenna 322 is connected to a LNA unit 320, which is further connectedto a bandpass filter 321. LNA unit 320 may be a high performanceamplifier with a typical gain of 15 dB and a noise figure of 1.5 dB withsufficient bandwidth to cover the appropriate portion of the spectrum.The bandpass filter 321 can be designed to pass all or a desired part ofthe cellular spectrum, or can be a bank of overlapping bandpass filters,covering the full spectrum of the interested cellular system, with a RFswitch, such that the selected band and bandwidth can be selectedmanually or automatically. Bandpass filter 321 is connected to frequencyconverter 318. The frequency converter 318 is capable of converting thecellular network operating spectrum band to a desirable part of theU-NII spectrum, and includes all components such as mixers and filtersfor correct operation. The frequency converter 318 is connected to theReverse-link User unit transmitter 316. The transmitter unit 316 isdesigned to operate in U-NII band and conforms to the FCC 47 CFRPart-15, subpart E regulations, and can be as simple as a singleamplifier operating at the desirable U-NII operation band, or a morecomplex transmitter with amplifiers and filters or even a WLANtransmitter such 802.11a. The transmitter unit 316 is connected toantenna 314. The selected portion of the U-NII band of operation for thereverse-link part of the booster is different to the selected portion ofthe U-NII band of operation for Forward-link part of the booster, andsufficiently apart, so that no substantial interference is experiencedfrom the operation of one link, to the other.

Antenna 312 is connected to the Reverse-link Network unit receiver 310,which is designed to receive the signal transmitted by unit 328. Thereceiver 310 which is connected to frequency converter 308, can be assimple as a single LNA operating at desirable U-NII band of deviceoperation frequency, or it can be better designed with additionalfunctionalities such as automatic gain control (AGC), multiple cascadedamplification stages, and variable channel select filters or even a WLANreceiver such as 802.11a (where the transmitter part of 802.11a is usedin the User unit 316). If automated gain control (AGC) is used inreceiver 310 and the unit is designed for CDMA cellular networks,performance is enhanced by selecting AGC bandwidth to be substantiallysmaller than the power control repetition rate of the CDMA system, forexample less than 1.5 kHz in WCDMA networks, so that AGC operation doesnot interfere with closed-loop power control. Frequency converter unit308, which is connected to receiver unit 310 and variable gain amplifierunit 306, converts the input signals, from U-NII band, to the cellularnetwork operating frequencies, and includes all components such asmixers and filters for correct operation. The frequency converter unit308 performs the opposite conversion operation of the frequencyconverter unit 318. The frequency converter 308 is connected to thevariable gain amplifier 306, operating at the cellular network operatingfrequency band. The variable gain amplifier 306 is connected to antenna304. Antenna 304 will be transmitting signals with substantially similarfrequencies to the frequencies transmitted by mobile unit 324.

The signal radiated by antenna 304, which is an amplified repeatedversion of the original incident signal received by antenna unit 322,will experience some loss in the power level, before returning andre-entering the antenna 322 again. The re-entered signal into antenna322 is termed “Up-link Returned-Signal” hereafter. The ratio of the rmssignal value of the Up-link Returned-Signal, to the rms value of theoriginal incident signal, at the output of the antenna 322 terminator,with system and propagation path delays between the antenna units 304and 322 removed, is the Up-link Returned-Signal path loss, and is termedhere as the “Up-link System Path Loss” and referred to as PL_(ul).

Further, the “Up-link System Link Gain” which here is referred to asG_(ul), is defined as “the ratio of the rms signal value at the input tothe antenna 304 terminator, to the rms signal value, at the antenna 322terminator, where the Up-link System Path Loss, PL_(ul), as definedabove, is infinite (for example no EM coupling path between antenna 304and antenna 322), and all the system and propagation path delays (fromantenna 322, through the system to antenna 304) are removed”.

The variable gain amplifier unit 306 gain is set such that Up-linkSystem Link Gain, G_(ul), is less than the Up-link System Path Loss,PL_(ul), by the amount of “Up-link gain margin”, dg_(ul), avoiding a“positive feed-back” loop in the system, for example,

G _(ul=) PL _(ul) −dg _(ul) (dB).

Note that all values of PL_(ul), G_(ul), and dg_(ul) are in dB. Thevalue of dg_(ul) ranges from 0 to PL_(ul), and can be assumed to be 3 dBfor the purposes of the description here. However, it is possible toselect better values for dg_(ul), where the system performance isoptimized further.

Usually the forward and the reverse links frequency pairs aresufficiently close, such that G_(ul) level is substantially similar toG_(dl) level, and PL_(ul) level is substantially similar to PL_(dl)level and dg_(ul) level is substantially similar to dg_(dl) level.

The unique booster unit identity code and optionally the device locationcan be transmitted to the cellular network. The information can be usedto locate a user in an indoor environment, for example by generating aheavily coded (protected), low bit rate data containing a long knownpreamble, the unique identity code, optionally the longitude, and thelatitude of the reverse-link Network unit 326. The information can thenbe pulse-shaped for low spectral leakage and superimposed on thereverse-link signal of a given channel by an appropriate modulationscheme, within the reverse-link Network unit 326. The choice of themodulation scheme depends on the operating cellular system. For example,for GSM, which enjoys a constant envelope modulation such as GaussianMinimum Shift Keying (GMSK), amplitude modulation (with low modulationindex) can be used. For CDMA systems with fast reverse-link powercontrol, Differential Binary Phase Shift Keying (DBPSK) can be used asthe modulation scheme. Extraction of information from the receivedchannel signal at base station may involve base station receivermodifications, but does not effect the normal operation of the cellularlink.

FIG. 4 shows an embodiment of a system 500 including the Network unit502, together with the User unit 504 in the same diagram. TheForward-link Network unit 514 (201 in FIG. 2) and the Reverse-linkNetwork unit 516 (326 in FIG. 3) are now in one unit, referred tohereafter as the Network unit 502. The Forward-link User unit 518 (202in FIG. 2) and the Reverse-link User unit 520 (328 in FIG. 3) are now inone User unit, referred to hereafter as the User unit 504. In FIG. 4,the transmit/receive antenna 203 in FIG. 2 and transmit/receive antenna304 in FIG. 3 are replaced by a single antenna 506 and duplex filter528. The duplex filter unit 528 is designed for optimum performance, andmeets specifications for cellular operation. Also, the transmit/receiveantenna 204 in FIG. 2 and transmit/receive antenna 312 in FIG. 3 arereplaced by a single antenna 508 and duplex filter 526. Further, thetransmit/receive antenna 205 in FIG. 2 and transmit/receive antenna 314in FIG. 3 are replaced by a single antenna 510 and duplex filter 524 inFIG. 4. Equally, the transmit/receive antenna 206 in FIG. 2 andtransmit/receive antenna 322 in FIG. 3 are replaced by a single antenna512 and duplex filter 522 in FIG. 4. The duplex filter unit 522 isdesigned for optimum performance, and complies with specifications forcellular operation. GSM system is a FDD system, and as such reverse-linkfrequencies are different to that of the forward-link frequencies. Insuch system a duplex filter provides appropriate functionality. However,if the Network unit 502 and the User unit 504 are designed for a TDDsystem, the duplexers 528 and 522 can be replaced by hybrid combiners or“circulators”. However, duplexers 526 and 524 are still used, sinceforward-link and reverse-link frequencies in the U-NII band are keptseparate (for example FDD). With minor modifications, it is possiblethat, instead of antennas 508 and 510, a coaxial cable (such as RG58 orIS inch heliax) is used to connect the Network unit 502 to the User unit504. In such an arrangement, where coaxial cable is used for the linkconnection, although still possible, up-conversion to U-NII bands issuperfluous, and the system can operate with the Forward andreverse-link signals kept at original cellular frequencies.

Transmit power level for the Network Unit 502 in the cellular band is inthe range of minus 10 dBm to 37 dBm with a down-link receiversensitivity of about −110 dBm to −120 dBm. Transmit power level for theUser Unit 504 in the cellular band is in the range of −20 dBm to 0 dBmwith an up-link receiver sensitivity of about −110 dBm to −120 dBm.

The described booster system typically operates satisfactorily inlimited scenarios, where the isolation between antennas 506 and 512 ismore than the up-link and down-link System Link Gains. To ensure thecorrect operation of the booster system in all propagation and operatingconditions, and without the need for the directional antennas, severalfeatures may be included in the system design.

-   -   1. Since both the Network unit 502 and the User unit 504 are for        most time stationary relative to each other, and possibly other        network elements such as base stations, antenna (space)        diversity is used for transmit and receive operations.    -   2. The signals transmitted by antenna 506, in the reverse-link,        are substantially at the same operating frequency band as the        reverse-link signals received by antenna unit 512. Equally, the        signals transmitted by antenna 512, in the forward-link, are        substantially at the same operating frequency band as the        forward-link signals received by antenna unit 506. As the        signals received by the Forward-link Network unit 514 are        transmitted to Forward-link User unit 518, via antenna units 508        and 510, and further, as the signal received by the Forward-link        User unit 518 is then amplified before the retransmission via        antenna unit 512, a feed-back loop, through the antennas 512 and        506, between the two Forward-link Network unit 514 and        Forward-link User unit 518 exists. Any gain in the loop causes        “positive feed-back”, which results in unstable operation, a        phenomenon that is also true for reverse-link operation of the        Network unit 502 and the User unit 504. To keep the two        feed-back loops in a stable operating region, in the        forward-link the Down-link System Link Gain, G_(dl), is less        than the Down-link System Path Loss, PL_(dl), by dg_(dl), so as        to avoid a “positive feed-back” loop in the system, for example        G_(dl=)PL_(dl)−dg_(dl) (dB). Equally, in the reverse-link, the        Up-link System Link Gain, G_(ul), is less than the Up-link        System Path Loss, PL_(ul), by dg_(ul), so as to avoid a        “positive feed-back” loop in the system. for example        G_(ul=)PL_(ul)−dg_(ul) (dB). The propagation losses, PL_(ul) and        PL_(dl), may be due to shadowing, distance and antenna radiation        pattern, and multipath propagation as well as wall penetration        loss. The levels of these propagation losses, PL_(ul) and        PL_(dl), are not readily available and are measured.    -   3. Continuous and correct operation of the Network unit 502 and        User unit 504 is monitored. Any operational problem at the        Network unit 502 or the User unit 504 can result in unwanted        transmissions in either forward or reverse (or both) links.        Further, the system may rely on radio channels operating at        unlicensed frequency bands, which are prone to interference from        other unlicensed devices. Also, operation of the Network unit        502 and the User unit 504 is coordinated. Therefore a        control-signaling channel is inserted between the two Network        502 and the User 504 units.    -   4. The local oscillators of the network unit 502 and the User        unit 504 are substantially similar in frequency, as any large        frequency error between the Network 502 and the User 504 units        will result in an unacceptable cellular link performance. In        some embodiments, a pilot signal can be transmitted in a control        link from the network unit 502 to the user unit 504 and used for        synchronization of local oscillators of the two units. In other        examples, an electric power supply waveform can be used for        synchronization of local oscillators in the two units.    -   5. In conventional repeaters sufficient isolation between        antennas corresponding to antennas 512 and 506 in the        illustrative embodiment is normally supplied by use of        directional antennas. Such directional antennas inherently have        large apertures, leading to large size antennas. To enable        maximum RF isolation between the antennas, advanced adaptive        temporal and spatial signal processing techniques are used,        enabling antenna directivity requirements to be relaxed.

Advanced Features

Illustrative advanced features include design solutions that are usefulin countering the enumerated problems.

FIG. 5 shows a system 600 including the Network unit 602 (502 in FIG. 4)with the new design features included. Two antennas 610 and 608 are usedfor antenna diversity, instead of a single antenna 506 in FIG. 4. Alsotwo antennas 636 and 638 are used for antenna diversity, instead of asingle antenna 512 in FIG. 4. Although any diversity-combining schemesuch as Maximal Ratio Combining or others can be used for the receiverchain, and transmit diversity schemes such as random phase change in oneor both antennas may be used for the transmitter chain, a simple schemethat is based on antenna switched diversity is suggested herein for thereceiver part. Switching may be continuous or based on received signalpower level. Therefore, the RF switch 612 connected to duplexers 614 and613 and the Forward-link Network unit 604 performs switching operationsfor the cellular receive operation of the Network unit 602. Also, the RFswitch 634 connected to antennas 636 and 638 and the duplex filter 632performs switching operations for the U-NII band transmit/receiveoperation of the Network unit 602. The duplex filters 614 and 613 arealso connected to antennas 610 and 608 on one side, and theComplex-Weight unit 648 on the other side, as well as the RF switch unit612. The complex-weight unit 648 is connected to power-splitter (hybridcombiner) 646 and the micro-controller 626. The power-splitter (hybridcombiner) 646 is connected to Reverse-link Network unit 606 via thedirectional coupler 618. In one embodiment, all directional couplers maybe 17 dB directional couplers. Also, the duplex filter 632 is connectedto Forward-link Network unit 604 via the directional coupler 630, andReverse-link Network unit 606 is connected via the directional coupler616. Hybrid combiners may otherwise be used in place of the directionalcouplers 618, 630 and 616. The Reverse-link Network unit 606 receiverunit 310 internal LNA maybe positioned before the directional coupler616, or the hybrid combiner replacement, in diagram 600 in aconfiguration that may be advantageous in some embodiments.

A calibration signal generator/transmitter unit 622 is coupled to thereverse-link transmitter path of the Network unit 602 via thedirectional coupler 618. The unit 622 supplies a channel-soundingsignal, which is used to establish the complex channel characteristicsbetween the Network unit 602 antennas 608 and 610, and the input to thecalibration signal receiver 620. The channel-sounding signal generatedby unit 622 is transmitted via the complex-weight unit 648 and thediversity antennas 610 and 608 with a maximum transmit level, which issubstantially below any expected signal level from cellular network (forexample 20 dB below the minimum expected cellular signal level). Thecombined transmitted channel-sounding signal level and the processinggain used in the calibration signal receiver unit 620 are equal to orless than the Up-link Gain Margin (dg_(ul)). The channel-sounding signalgenerated by unit 622 is a direct-sequence spread spectrum signalmodulated by a known Pseudo Random (PN) code with a known code phase(referred to hereafter as “own code” phase) and with a chipping ratecomparable to the forward and reverse links of the Network unit 602 andUser unit 702 (in FIG. 6) operating bandwidths (e.g. 5 Mchips/s for 5MHz bandwidth) and a minimum code length to supply sufficient processinggain, which also has a code time duration longer than the maximumexpected path delay. A code length of 1000 chips is adequate for mostscenarios. The channel-sounding signal can be transmitted continuouslyor transmitted only when required. The code phases are selected suchthat the minimum code phase difference is larger than the maximumexpected path delay, measured in multiple number of chips, and afterthat the code phases should be multiple integer of the minimum codephase. The calibration signal receiver unit 620 is coupled to thereverse-link receive path of the Network unit 602 by directional coupler616. The calibration signal receiver unit 620, using the known PN codeand the transmit code phase, detects and demodulates thechannel-sounding signal transmitted by unit 622, which enters thereverse-link path via the closed-loop mechanism that exists between theNetwork unit 602 and the User unit 702 in FIG. 6, shown as user unit 504in FIG. 4. The calibration signal receiver unit 620 is configured toestablish the received signal strength and phase—the complex channelimpulse response that exists between the Network unit 602 combinedoutputs of antennas 608 and 610 and the input to the calibration signalreceiver 620. The calibration signal receiver unit 620 establishesreceived signal strength and phase either by correlation operation,similar to a RAKE receiver path searcher, or by matrix inversionoperation on an appropriate block of sampled received signal, discussedin more detail in appendix A. The calibration signal receiver unit 620includes many sub-units, including a frequency converter, to return thecalibration signal to base-band frequencies and other units such as A/Dconverters and base-band processors to perform base-band algorithmswhich are not shown in the diagram. The PN code phase can be assigneduniquely, or drawn according to a random algorithm, such that theprobability of two units having the same code phase can be very low.Other code offset assignment strategies are also possible, such asdynamic assignment, where the code offset is selected if no such offsetwas detected in that geographical area. The feature enables thecalibration signal receiver 620 to be able to scan and receive “othercode” phases, and hence establishing whether any other signal couples toor from other units that may be operating in the same geographical area.More than one code phase can be used to establish the complex channelimpulse response so that the probability of detection by other systemsis increased. The PN code used for the channel-sounding signal can bemodulated with information about the identity of the Network unit 602.The carrier frequency of the transmitted channel-sounding signal can beat the operating cellular frequency band. However, carrier frequenciesin other bands, such as ISM band at 2.4 GHz, may be used fortransmission of the channel-sounding signal. When carrier frequencies inthe other bands are used, the calibration signal generator andtransmitter 622 carrier frequency is placed as near as possible to theoperating frequency band. The chipping rate and the transmit power ofthe channel-sounding signal PN code are implemented in a manner that thechannel-sounding signal complies with the FCC 47 CFR Part-15 rules. TheISM band is not the same as the cellular operating band, but issufficiently close to enable the system to converge the spatialalgorithm weights and establish weights W₀ and W₁ used in thecomplex-weight unit 648. Any antenna and propagation differences inaverage signal power and antenna behavior between the ISM and cellularoperating bands can be taken into account in an operatingimplementation.

The Equipment ID and reference frequency unit 624 basically generates aBinary Phase Shift Keying (BPSK) signal, modulated by the equipment IDnumber and placed at a suitable part of U-NII band, and is coupled inthe transmitter path of the forward-link of the Network unit 602 via thedirectional coupler 630. The unit is “frequency locked” to the localoscillator of the Network unit 602. The carrier frequency of the signalis selected to avoid an unacceptable interference to the main cellularsignal in the transmit path of the forward-link of the Network unit 602,but is sufficiently close for an optimum transmission bandwidth. Wherethe Network unit 602 and the User unit 702 use the mains electricitysupply for their operations, the 60 Hz or 50 Hz mains oscillations canbe used to “lock” the local oscillators of the two units to a commonfrequency source. The 60 Hz or 50 Hz mains oscillations are converted,by suitable circuitry, to the selected frequency for the operation ofthe Network unit 602 and the User unit 702.

The Control Link unit 628 is a radio link between the two, Network unit602 and the User unit 702 in FIG. 6. It may be a simple proprietary linkthat operates in one of the unlicensed band of frequencies, or may be anin-band control signaling, multiplex with the cellular signal path. Itmay also be a standard wireless link such as 802.11b, 802.11a orBluetooth, designed to operate in unlicensed frequency band. The controllink unit 628 is connected to micro-controller unit 626, and is able tocommunicate through an appropriate interface. The control link unit 628is also connected to antenna 644 and 642 for transmission and receptionof the control signals. If operating bandwidth and frequencies allow,with minor modifications to init 602, antenna units 636 and 638 can alsobe used for the operation of control link unit 628. In some embodiments,the User unit 702 can be a very simple device with all signal processingand control functionalities supported in the Network unit 602. If so,the control link unit 628 can be eliminated or may implement very simplecontrol signaling such as in-band frequency tones to set the systembandwidth and gain in the User unit 702. Provided that the antennabandwidth allows, with minor modifications to unit 602, antenna units636 and 638 can also be used for control link unit 628 operations.

Micro-controller unit 626 may be a simple micro-processor such as ARM7or ARM9 with appropriate memory and interfaces. The micro-controllerunit 626 is controlling the operation of the Network unit 602, and mayperform some additional signal conditioning and processing such assignal level averaging, estimation, and adaptive algorithms such asLeast Mean-Square (LMS) and Recursive Least Squares (RLS), where useful.Operations of micro-controller unit 626 include setting the operatingbandwidth and set the weights W₀ and W₁ to communicate and control theUser unit 702 in FIG. 6 via the control link unit 628, communicate andcontrol the calibration signal generator and transmitter 622 andcalibration signal receiver 620, operate switching for the receiverantenna diversity, and monitor the correct operation of the Network unit602 and User unit 702. Other tasks of the micro-controller 626 aredisclosed as examples in FIGS. 8A, 8B, 8C, and 8D. Micro-controller unit626 is connected to units 627, 628, 622, 606, 604, 620, 648 and 624, aswell as the RF switches 634 and 612. The micro-controller 626, using thecomplex channel impulse response at the output of the calibration signalreceiver unit 620 and using Least Mean-Square (LMS), Recursive LeastSquares (RLS), QR-RLS, or QR decomposition, computes values of thecomplex weights, W₀ and W₁ such that the received complex channelimpulse response at the output of the calibration signal receiver unit620 is reduced or minimized in magnitude. With such transmit weightsarrangement, the RF isolation for up-link frequencies between theNetwork unit 602 and the User unit 702 is adapted within the propagationchannel, enabling the maximum possible overall ERP (Effective RadiatedPower) from antennas 608 and 610, and hence the maximum coveragefootprint.

Units 628, 622, 606, 604, 620, 624 are all connected to local oscillatorunit 640, and derive clock and reference frequencies from the localoscillator 640 signal. A simple user interface unit 627, for example akeypad, simple dipswitch or similar device, is connected tomicro-controller unit 626. The Network unit 602 has a unique “identitycode”, which can be set by the user interface unit 627, is accessible bythe micro-controller unit 626, and can be communicated to the User unit702 micro-controller unit 728 or any other User units that may be withinthe operating range of Network unit 602.

FIG. 6 shows an embodiment of a repeater 700 including the User unit 702(504 in FIG. 4) with the new design features included. Two antennas 734and 736 are used for antenna diversity, instead of a single antenna 512in FIG. 4. Also, two antennas 704 and 706 are used for antennadiversity, instead of a single antenna 510 in FIG. 4. Although anydiversity-combining scheme such as Maximal Ratio Combining, etc. can beused for the receiver chain, and transmit diversity schemes such asrandom phase change in one or both antennas for the transmitter chain, asimple scheme that is based on antenna switched diversity can beimplemented for the receiver. The switching can be continuous or basedon received signal power level. Therefore, the RF switch 732 connectedto duplexers 754 and 756 and the Reverse-link User unit 726 performsswitching operations for the cellular receive operation of the User unit702. Also, the RF switch 712 connected to antennas 704 and 706 and theduplex filter 714 performs switching operations for the U-NII bandtransmit/receive operation of the User unit 702. The duplex filters 754and 756 are also connected to antennas 734 and 736 on one side, theComplex-Weight unit 748 on the other side, as well as the RF switch unit732. The complex-weight unit 748 is connected to power-splitter (hybridcombiner) 745 and the micro-controller 728. The power-splitter (hybridcombiner) 745 is connected to Forward-link User unit 724 via thedirectional coupler 746. All directional couplers in may be 17 dBdirectional couplers. Also, the duplex filter 714 may be connected toForward-link User unit 724 via the directional couplers 740 and 718, andalso connected to Reverse-link User unit 726. The Forward-link User unit328 receiver 210 internal LNA may be positioned prior to the directionalcouplers 718 and 740 in diagram 700, a configuration that may enhanceperformance.

A calibration signal generator/transmitter unit 744 is coupled to theforward-link transmitter path of the User unit 702 via the directionalcoupler 746. The unit 744 generates a channel-sounding signal, which isused to establish complex channel characteristics between the User unit702 antennas 734 and 736, and the input terminal to the calibrationsignal receiver 742. The channel-sounding signal generated by unit 744is transmitted via the complex-weight unit 748 and the diversityantennas 734 and 736 with a maximum transmit level that is substantiallybelow any expected signal level from cellular network, for example 20 dBbelow the minimum expected cellular signal level. The combinedtransmitted channel-sounding signal level and the processing gain usedin the calibration signal receiver unit 742 is less than or equal toDown-link Gain Margin, dg_(dl). The channel-sounding signal generated byunit 744 is a direct-sequence spread spectrum signal modulated by aknown Pseudo Random (PN) code with a known code phase, for exampletermed an “own code” phase, and having a chipping rate comparable to theforward and reverse links of the User unit 702 and Network unit 602shown in FIG. 5 operating bandwidths of, for example 5 Mchips/s for 5MHz bandwidth. The PN code further may have the minimum code lengthsufficient to supply suitable processing gain and which exceeds themaximum expected path delay. A PN code length of 1000 chips is adequatefor most scenarios. The channel-sounding signal can be transmittedcontinuously or transmitted only when evoked by conditions. Code phasesare selected so that the minimum code phase difference is larger thanthe maximum expected path delay measured in multiple chips. Subsequentcode phases can be a multiple integer of the minimum code phase. Thecalibration signal receiver unit 742 is coupled to the forward-linkreceive path of the User unit 702 by directional coupler 740 and usesthe known PN code and the transmit code phase to detect and demodulatethe channel-sounding signal transmitted by unit 744. Thechannel-sounding signal enters the reverse-link path via the closed-loopmechanism between the User unit 702 and the Network unit 602 in FIG. 5,also shown as unit 502 in FIG. 4. The calibration signal receiver unit742 adapted to establish the received signal strength and phase. Acomplex channel impulse response exists between the User unit 702combined outputs of antennas 734 and 736, and the input terminal to thecalibration signal receiver 742. The calibration signal receiver unit742 sets received signal magnitude and phase either by correlationoperation, for example similar to a RAKE receiver path searcher, or bymatrix inversion operation on an appropriate block of sampled receivedsignal, as disclosed in appendix A. The calibration signal receiver unit742 includes many sub-units, such as a frequency converter that returnsthe calibration signal to base-band frequencies and other units such asA/D converters and base-band processors to perform base-band algorithms.The sub-units are not shown in the diagram. The PN code phase can beassigned uniquely or drawn according to a random algorithm so that theprobability of two units having the same code phase is very low. Othercode offset assignment strategies are also possible. For example,dynamic assignment may be used so that the code offset is selected toavoid other such offsets in the same geographical area. Dynamicassignment enables the calibration signal receiver 742 to scan andreceive “other code” phases and hence establish whether any other signalcouples to or from other units that may be operating in the samegeographical area. Further, more than one code phase can be used toestablish the complex channel impulse response so that the probabilityof detection by other systems is increased. The PN code used for thechannel-sounding signal can be modulated with information about theidentity of the User unit 702. The carrier frequency of the transmittedchannel-sounding signal may be at the operating cellular frequency band.However, carrier frequencies in other bands such as ISM band at 2.4 GHzmay be used for transmission of the channel-sounding signal. Usage ofthe other bands enables the calibration signal generator and transmitter744 carrier frequency to be placed as near as possible to the operatingfrequency band. The chipping rate and the transmit power of thechannel-sounding signal PN code are selected so that thechannel-sounding signal complies with the FCC 47 CFR Part-15 rules. TheISM band, although different from the cellular operating band, issufficiently close to enable the system to converge the spatialalgorithm weights, and establish the weights W₀ and W₁ used in thecomplex-weight unit 748. Any antenna and propagation differences inaverage signal power and antenna behavior between the ISM and cellularoperating bands can be investigated in the design phase and taken intoaccount in the final system design.

The Reference signal receiver unit 716, which is capable of receivingthe transmitted signal generated by the equipment ID and referencefrequency unit 624 in FIG. 5, is connected to the directional coupler718. The receiver is capable of extracting the reference frequency andthe ID code transmitted by the Network unit 602 equipment ID andreference frequency generator 624. The extracted reference frequency isthen used to provide a reference local oscillator 722. The directionalcoupler 718 is connected to the Forward-link User unit 724. Reverse-linkUser unit 726 is connected to duplex filter 714. The reference signaland the local oscillator unit 722 can alternatively be based on thecontrol link unit 720 oscillator, if the unit 726 is capable of lockingto the received signal carrier frequency which has been transmitted bycontrol link unit 628 of the Network unit 602.

The Control Link unit 720 is a radio link between the two, Network unit602 and the User unit 702. It may be a proprietary link that operates inone of the unlicensed band of frequencies, or may be a standard wirelesslink such as 802.11b, 802.11a or Bluetooth, designed to operate inunlicensed band. The control link unit 720 is connected tomicro-controller unit 728, and is able to communicate through anappropriate interface. The control link unit 720 is also connected toantennas 708 and 710 for transmission and reception of the controlsignals. Note that provided that the antenna bandwidth and operatingfrequency allow, with minor modifications to unit 702, antenna units 704and 706 can also be used for the control link unit 720 operations.

Micro-controller unit 728 is a simple microprocessor such as ARM7 orARM9 with appropriate memory and interfaces. The micro-controller unit728 is controlling the operation of the User unit 702 and may performsome additional signal conditioning and processing such as signal levelaveraging and estimation and adaptive algorithms such as LMS and RLS insuitable conditions. The micro-controller unit 728 may set operatingbandwidth and set weights W₀ and W₁ to communicate and control theNetwork unit 602 in FIG. 5 via the control link unit 720, and tocommunicate and control the calibration signal generator and transmitter744 and calibration signal receiver 742. The micro-controller unit 728may also operate switching for receiver antenna diversity and monitorthe correct operation of the User unit 702. Other tasks of themicro-controller 728 are disclosed in examples depicted in FIGS. 8A, 8B,8C, and 8D. Micro-controller unit 728 is connected to units 720, 742,744, 716, 748, 726, and 724, as well as the RF switches 732 and 712. Themicro-controller 728 may use a complex channel impulse response at theoutput of the calibration signal receiver unit 742 and use LeastMean-Square (LMS), Recursive Least Squares (RLS), QR-RLS, or QRdecomposition to compute optimum values of complex weights W₀ and W₁such that the received complex channel impulse response at the output ofthe calibration signal receiver unit 742 is reduced or minimized. Withthe disclosed transmit weights arrangement, the RF isolation fordown-link frequencies between the User unit 702 and the Network unit 602is adapted within the propagation channel, enabling a maximum possibleoverall ERP (Effective Radiated Power) from antennas 734 and 736 and amaximum coverage footprint.

Units 720, 726, 724, 742, 744 and 728 are depicted connected to localoscillator unit 722 and derive clock and reference frequencies from thelocal oscillator 722 signal. A simple user interface unit 721, forexample a keypad or simple dipswitch, may be connected tomicro-controller unit 728. The Network unit 702 has a unique “identitycode” which can be set by the user interface unit 721, is accessible tomicro-controller unit 728, and can be communicated to the Network unit602 micro-controller unit 626 or other Network or User units that may bewithin the operating range of User unit 702.

Techniques, such as the use of vertical polarization for antennas units610 and 608, and horizontal polarization for antennas 734 and 736 canfurther improve the system performance. It is also possible to improvesystem performance by the use of directional antennas, as inconventional booster and repeater systems.

The unique Network unit 602 identity code and optionally device locationcan be transmitted to the cellular network. The information can be usedto locate a user in an indoor environment, for example by generating aheavily coded (protected), low bit rate data, containing a long knownpreamble, the unique identity code and optionally the longitude and thelatitude of the Network unit 602. The information can then bepulse-shaped for low spectral leakage and superimposed on thereverse-link signal of a given channel by an appropriate modulationscheme, within the Network unit 602. The choice of the modulation schemedepends on the operating cellular system. For example, for GSM, whichenjoys a constant envelope modulation such as Gaussian Minimum ShiftKeying (GMSK), amplitude modulation (with low modulation index) can beused. For Code Division Multiple Access (CDMA) systems, with fastreverse-link power control, Differential Binary Phase Shift Keying(DBPSK) can be used as the modulation scheme. The extraction of theabove mentioned information from the received channel signal at basestation may involve base station receiver modifications, but does noteffect the normal operation of the cellular link.

An example of the above system operation is shown in FIGS. 7A, 7B, 7C,7D, 8A, 8B, 8C, and 8D. FIGS. 7A, 7B, 7C, and 7D are the systemoperation flow diagrams for the Network unit 602 and FIGS. 8A, 8B, 8C,and 8D are the flow diagrams for the User unit 702. The examples do notinclude all possible functionalities for the complete operation of theNetwork unit 602 and User unit 702. The examples show an example ofminimum control flows for basic operation of the Network unit 602 andthe User unit 702. Two independent control flow operations can beexecuted concurrently on the micro-controller 626. A first control-flowestablishes normal operation of the booster. A second control flowmonitors operation of the control link between the Network unit 602 andthe User unit 702. On “power-up”, “reset”, or a “Stop” instruction,Network unit 602 sets complex-weight unit 648 weights W₀ and W₁ to an“Initial” value by default. The “Initial” values of the weights arevalues allowing minimum power radiation from the two antennas 608 and610 with no phase differential between the two radiated fields, forexample broadside radiation. On “power-up” or “reset” instructions ofthe Network unit 602, assuming the “identity code” of the interestedUser unit 702 is known or pre-entered into the Network unit 602 via theuser interface unit 627), the micro-controller unit 626 starts thecontrol-flow 802 in FIG. 7A. The micro-controller unit 626 instructs thecontrol link unit 628 to establish 804 link with the User Unit 702. Thecontrol link unit 628, using appropriate protocols, continues attemptsto establish a communication link with the control unit 720 of the Userunit 702 until such link is established 806. The micro-controller unit626 selects 808 the U-NII band of operation, if desired, and instructsthe calibration signal receiver unit 620 to attempt to receive 810 allthe possible code offsets in the U-NII frequency band, ensuring nosignal paths from other User units are operational in the immediate areainto the Network unit 602 and facilitating selection of an unused codeoffset and transmission channel. If an unintended signal path exists 812between the Network unit 602 and other operating User units, dependingon the severity of the coupling path and the strength of the “otherunits” received channel-sounding signal(s) strength, several differentactions can be taken after comparison of the received signal Signal toNoise Ratio (SNR) with threshold SNR_(th), which is based on maximumallowed interference plus noise level 814 for acceptable performance:

-   -   1) If the strength of the received channel-sounding signal(s)        from other User units is below the threshold SNR_(th),        indicating NO interference with the operation of the Network        unit 602 and User unit 702, the micro-controller 626 proceeds as        normal to action 824.    -   2) If the strength of the received channel-sounding signal(s)        from other User units is above the threshold SNR_(th),        indicating interference with the operation of the Network unit        602 and User unit 702, the Network unit 602 will try to select        another U-NII frequency band of operation (step 816), and if        more U-NII operating band available, steps 808, 810, and 812 are        repeated (step 816).    -   3) If the strength of the received channel-sounding signal(s)        from other User units is above the threshold SNR_(th),        indicating interference with the operation of the Network unit        602 and User unit 702, and no new clean U-NII operating        frequency band can be found, the Network unit 602 will issue an        appropriate error signal (block 818) and instruct User unit 720        to stop operation (step 9), and the Network unit 602 stops        operation (step 822).

After successful establishment of a control link between the Networkunit 602 and the User unit 702, and successful selection of a U-NIIoperation band, micro-controller 626, via the control link unit 628,instructs the User unit 702 to scan 824 for possible code offsets in theselected U-NII band of frequencies. Micro-controller 626 waits for ascan report from User unit 702. If any other units are operating nearbyand are detected by the User unit 702, micro-controller 626 seeks 816another U-NII band of frequencies and follows the subsequent steps asdescribed. If no other operational unit is detected by the User unit702, the micro-controller 626 selects 828, as shown in FIG. 7B, anunused Code-Offset, called an “own code” phase. The micro-controller626, via the control link unit 628, informs 830 the User unit 702 of theselected “own code” phase. After entering 832 the network unit 602 into“channel-sounding” mode, micro-controller 626, via the control link unit628, instructs User unit 702 to enter 834 the “channel-sounding” aswell. In “channel-sounding” mode the diversity switches 612 and 634 inNetwork unit 602, and 732 and 712 in User unit 702, are kept in thecurrent position, for example not switching. Micro-controller 626, viathe control link unit 628, instructs 836 the User unit 702 to commencewith channel-sounding operation. Micro-controller 626 sets 838 thecomplex-weight unit 648 weights W₀ and W₁ to the “Initial” value.Micro-controller 626 instructs 840 calibration signal generator andtransmitter unit 622 to commence transmission with the specified “owncode” phase. Micro-controller 626 also instructs 842 the calibrationsignal receiver unit 620 to attempt to receive the channel-soundingsignal for the above mentioned code offset, used by the transmitter unit622. If no substantial channel-sounding signal is detected 844 with thespecified set of weights of the complex-weight unit 648, and Up-linkSystem Link Gain, G_(ul), is less than the specified maximum allowedsystem gain 846, micro-controller 626 modifies and issues 848 new weightvalues to complex-weight unit 648 such that the transmit power of thechannel-sounding signal is increased by a predetermined step size, dG,while keeping the relative phases of the weights W₀ and W₁ the same.Actions 842, 844, 846 and 848 are repeated until a substantialchannel-sounding signal is detected or the maximum allowed system gainis reached. If maximum allowed system gain is reached, the most recentweights are maintained 850 unchanged as the most optimum weights fornormal operation. If maximum allowed system gain is not reached andsubstantial channel-sounding signal is present at the output of thecalibration signal receiver 620, an adaptive convergence algorithm suchas LMS is used to further modify 852 the weights W₀ and W₁ such that thechannel-sounding signal power is reduced or minimized. New weights areissued 854 to the complex-weight unit 648 for transmission of thechannel-sounding signal. If the weights are sufficiently converged 856,control-flow proceeds, otherwise actions 840 to 856 are repeated. Aftersuccessful convergence of the Network unit 602 weights W₀ and W₁,micro-controller 626 checks 858 and, if warranted, waits 860 forconfirmation of User unit 702 weight convergence. After successfulconvergence of both Network unit 602 and User unit 702 weights W₀ andW₁, micro-controller 626 instructs 862 the user unit 702 to exit thechannel-sounding mode and exit 864 channel sounding mode.Micro-controller 626 instructs 866 calibration signal receiver 620 tocontinue to receive the channel-sounding signal transmitted by thecalibration signal transmitter 622. If the safe average channel-soundingsignal power level is exceeded 868 for a substantial amount of time,micro-controller 626 control flow goes to action 832, and starts thechannel-sounding processes again. If the average channel-sounding signalpower level is within the expected range, the calibration signalreceiver 620 is instructed to receive and detect 870 channel-soundingsignals with all other possible code offsets. If no channel-soundingsignal with substantial average signal power level is detected, themicro-controller 626 checks 874 to determine whether any messages orproblems are reported from the User unit 702. If no messages arepresent, microcontroller 626 returns to action 866. If achannel-sounding signal with substantial average signal power level isdetected or a problem is reported by the User unit 702, themicro-controller 626 goes 876 to action 802 and begins the control flowprocess again. To accelerate search and detection of other code offsets,two or more replicas of the calibration signal receiver 620 may beimplemented, so that the “own code” detection can be continuous anduninterrupted, and other receiver replicas can scan for “other code”offsets.

The second control-flow operation is shown in FIG. 7D. The secondoperation checks the quality and performance of the control links of thecontrol units 628 and 720 operation, by monitoring such quantities asBit Error Rate (BER), Signal to Noise Ratio (SNR), background noise andinterference (step 860). If the operation of the link is notsatisfactory (step 882), an error signal is flagged (step 884), andcomplex-weight unit 648 weights W₀ and W₁ are set to the “Initial” value(step 886), and the User unit 702 is instructed to do the same (Step888), and finally the micro-controller 626 returns to step 802 (step890).

FIGS. 7A, 7B, 7C, and 7D are system operation flow diagrams for the Userunit 702. Two independent control flow operations are executedconcurrently on the micro-controller 728. The first control-flowestablishes normal operation of the booster. The second control-flowmonitors correct operation of the control link between the User unit 702and the Network unit 602. On “power-up”, “reset”, or a “Stop”instruction, User unit 702 sets the complex-weight unit 748 weights W₀and W₁ to “Initial” value by default. “Initial” weight values aredefines ad values that enable minimum power radiation from the twoantennas 734 and 736 with no phase differential between the two radiatedfields, for example broadside radiation. On “power-up” or “reset”instruction of the User unit 702, assuming the “identity code” of theinterested Network unit 602 is available or pre-entered into the Userunit 702 via the user interface unit 721, the micro-controller unit 728begins 902 the control-flow in FIG. 8A. The micro-controller unit 728instructs 904 control link unit 720 to establish communication with theNetwork Unit 602. The control link unit 720 uses appropriate protocolsand continues attempts to establish 906 a communication link withcontrol unit 628 of the Network unit 602 until the link is established.Micro-controller unit 728 attempts 908 to detect instruction messagesfrom the Network unit 602 and continues to do so until an instruction isdetected 910. On the receipt of the first instruction from the Networkunit 602, micro-controller unit 728 attempts to determine theinstruction content. The first analysis 912 determines whether thereceived instruction is the “Stop” instruction. For the “Stop”instruction, the micro-controller unit 728 sets 914 the complex-weightunit 648 weights W₀ and W₁ to the “Initial” value and continues todetect new instructions. If the instruction is “Scan for all code offsetin the specified U-NII band” 916, the micro-controller unit 728instructs the Calibration signal receiver unit 742 to scan 918 for allthe possible code offsets in the specified frequency band, ensuring nosignal paths exist from other Network units operational in the immediatearea into the User unit 702 and facilitating selection of an unused codeoffset and transmission channel. User unit 702, via the control link 720informs 920 the Network unit 602 of scan results for code offsets withsignificant signal level and waits for a new instruction. Themicro-controller unit 728 awaits 908 a new instruction from Network unit602.

If the new instruction is “Enter the channel sounding mode” 922,micro-controller unit 728 enters 924 the mode by setting the diversityswitches 732 and 712 to a fixed, non-switching state. Micro-controller728 sets 926 complex-weight unit 748 weights W₀ and W₁ to the “Initial”value. Micro-controller 728 instructs calibration signal generator andtransmitter unit 744 to commence transmission 928 with the specified“own code” phase. The micro-controller 728 also instructs thecalibration signal receiver unit 742 to attempt to receive 930 thechannel-sounding signal for the above mentioned code offset used by thetransmitter unit 744. If no substantial channel-sounding signal isdetected with the specified set of weights of the complex-weight unit748 and Down-link System Link Gain G_(dl) is less than the specifiedmaximum allowed system gain 934, micro-controller 728 modifies andissues 936 new weight values to complex-weight unit 748 so that thetransmit power of the channel-sounding signal is increased by apredetermined step size dG while maintaining 936 relative phases of theweights W₀ and W₁. Actions 930, 932, 934 and 936 are repeated until asubstantial channel-sounding signal is detected or the maximum allowedsystem gain is reached. If maximum allowed system gain is reached, themost recent weights are maintained 944 as the most optimum weights fornormal operation. If maximum allowed system gain is not reached andsubstantial channel-sounding signal exists at the output of thecalibration signal receiver 742, an adaptive convergence algorithm suchas LMS is used to further modify 938 weights W₀ and W₁ such that thechannel-sounding signal power is reduced or minimized. New weights areissued 940 to the complex-weight unit 748 for transmission of thechannel-sounding signal. If weights are sufficiently converged,control-flow proceeds to next action, otherwise actions 928 to 942 arerepeated. After the successful convergence of the User unit 702 weightsW₀ and W₁, micro-controller unit 728 informs 946 the Network unit 602and confirms the convergence of the weights. Micro-controller unit 728awaits an instruction to exit the channel-sounding mode in actions 948and 950. After detection of the instruction “Exit channel-soundingmode”, micro-controller unit 728 exits 952 the operating mode andinstructs the calibration signal receiver 742 to continue to receive 954the channel-sounding signal transmitted by the calibration signaltransmitter 744.

If the safe average channel-sounding signal power level is exceeded fora substantial amount of time 956, micro-controller 728 sets 926 thecomplex-weight unit 748 weights W₀ and W₁ to the “Initial” value andinforms 964 the Network unit 602, and returns to action 908. If theaverage channel-sounding signal power level is within the expectedrange, the calibration signal receiver 742 is instructed to receive anddetect 958 channel-sounding signals with other possible code offsets. Ifa channel-sounding signal with substantial average signal power level isdetected, the micro-controller 728 goes 960 to action 962. If no otherchannel-sounding signal with substantial average signal power level isdetected, the micro-controller 728 returns to action 908. To acceleratethe search and detection of other code offsets, two or more replicas ofthe calibration signal receiver unit 620 may be included so that the“own code” detection can be continuous and uninterrupted. Other receiverreplicas may scan for “other code” offsets.

A second control-flow operation is shown in FIG. 8D. The secondoperation checks the quality and performance of the control links of thecontrol units 720 and 628 by monitoring 970 quantities such as Bit ErrorRate (BER), signal to noise ratio (SNR), background noise andinterference. If the operation of the link is not satisfactory 972, anerror signal is flagged 974 and the complex-weight unit 748 weights W₀and W₁ are set 976 to the “Initial” value. Network unit 602 is informed977 before the micro-controller 728 returns 978 to action 902.

The description is merely an example a system implementation. Otherpossible methods and solutions may be implemented and some descriptionof control signaling is omitted. Several points may be noted.

-   -   1. The Network unit 602 can control several User units, such as        the User unit 702. In such setups, the example control flow,        shown in FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C, and 8D may be        modified so that the Network Unit 602 can initialize each User        unit independently at first and together in a final action. In a        configuration with multiple User units such as 702, the Network        unit 602 weights may be converged for the User unit that has the        minimum Up-link System Path Loss PL_(ul), with the Network unit        602. Therefore each User unit 702 in a booster network may have        a unique code phase.    -   2. Another modification used for a configuration with multiple        User units 702, final weight convergence of the units in a        booster network, including both Network and User units, may be        performed with User units under control of the Network unit 602        active in the channel-sounding operation. Accordingly, combined        signal power levels do not exceed the safe limit. If combined        signal from the User Units exceeds the acceptable level for        either of the reverse or forward system links, the appropriate        weights have to be modified in iterative step increments to a        level at which the maximum allowed system link gains of the        forward and the reverse links are met.    -   3. Although the forward link direction signal path in both the        Network unit 602 and the User unit 702 is always active to boost        the beacon for example for Broadcast Control Channel (BCCH) in        Global System for Mobile Communications (GSM) transmissions of        the base stations, the reverse-link signal path of the Network        unit 602 and the User unit 702 need not be active unless a        substantial signal level is detected, based on the presence of        uplink or gated signal. Care is taken that the reverse-link        gated operation does not interfere with the channel-sounding        signal path and unit 622 and 620 communications. Therefore, the        gated operation is a continuous operation during the        channel-sounding process with channel sounding carried out on        regular bases.    -   4. Modifications in hardware and control software may be        implemented to merge the Network unit 602 and the User unit 702        into a single unit, connected “back-to-back”. Design and        operation of the back-to-back option is described with reference        to FIG. 11.    -   5. The unique Network unit 602 identity code and optionally        device location can be transmitted to the cellular network. The        information can be used to locate a user in an indoor        environment, for example by generating a heavily coded        (protected), low bit rate data, containing a long known        preamble, the unique identity code and optionally the longitude        and the latitude of the Network unit 602. The information can        then be pulse-shaped for low spectral leakage and superimposed        on the reverse-link signal of a given channel by an appropriate        modulation scheme, within the Network unit 602. The choice of        the modulation scheme depends on the operating cellular system.        For example, for GSM, which enjoys a constant envelope        modulation such as Gaussian Minimum Shift Keying (GMSK),        amplitude modulation (with low modulation index) can be used.        For Code Division Multiple Access (CDMA) systems, with fast        reverse-link power control, Differential Binary Phase Shift        Keying (DBPSK) can be used as the modulation scheme. The        extraction of the above mentioned information from the received        channel signal at base station may involve base station receiver        modifications, but does not effect the normal operation of the        cellular link.    -   6. The system design may also include Closed-loop power control        between the Network unit 602 and User unit 702 for unlicensed        band (U-NII) operation both in forward and reverse links.        Closed-loop power control may be based on very low-rate, for        example 10 Hz, differential or absolute power control commands        based on received signal power to increase or reduce the U-NII        band transmission powers so that only sufficient power is        transmitted from the antennas 636, 638 on the Network unit 602        side and antennas 704 and 706 on the User unit 702 side for        correct operation. Variable gain amplifiers may be used for        transmission of the U-NII band both in the Network unit 602 and        the User unit 702. Closed-loop power control messages may be        exchanged between the Network unit 602 and the User unit 702 via        the control link units 628 and 720 in forward and reverse-links.    -   7. On the Network unit 602 side, once the complex-weight unit        648 weights W₀ and W₁ are converged spatial dither may be        superimposed on the antenna radiation pattern so that multipath        standing wave patterns are sufficiently disturbed to include        diversity gain on the Up-link. A second set of weights may be        converged to maintain the spatial position of the “nulls” while        changing the radiation pattern sufficiently to create antenna        radiation pattern diversity. Weights can be converged by first        performing direction finding, for example using a discrete        Fourier transform (DFT) on the original weights to identify the        ‘Null” position and forming new weights using algorithms such as        Minimum-Variance Linear-Constraint Beam-forming algorithms        (MVLCBF) with the constraint being the position of the spatial        “Null”. Repeated switching between the two sets of weights        creates antenna pattern diversity gain on the up-link. Similar        structures and techniques can be implemented on Down-link path        of the User unit 702.    -   8. In the illustrative embodiment of the Network unit 602 and        the User unit 702, only two sets of complex weights W₀ and W₁        are used in the complex-weight units 648 and 748 since two        diversity antennas are readily available at both units. In other        embodiments, in both the Network unit 602 and in the User unit        702 more than two antennas and hence more than two weights can        be used with minor modifications from the disclosed structures        and techniques.    -   9. Although the complex-weight units 648 in the Network unit 602        and complex-weight units 748 in the Network unit 702 are used        for transmitter beam-forming, similar complex weight units may        be used at the input terminals to the receivers of the        Forward-link Network unit 604 in the Network unit 602 and        Reverse-link User unit 726 in the Network unit 702 so that        receiver beam-forming can also be performed. The receiver weight        convergence can be based on similar procedure as for the        transmitter implementation with only minor changes.    -   10. Weights W₀ and W₁ of the complex-weight units 648 in the        Network unit 602 and complex-weight units 748 in the Network        unit 702 may be converted with the Reverse-link Network unit 606        in the Network unit 602 and Forward-link User unit 724 in the        Network unit 702 completely “OFF” or disabled so that cellular        signals are not repeated or transmitted. Accordingly,        convergence of the weights W₀ and W₁ of the complex-weight units        648 in the Network unit 602 and complex-weight units 748 in the        Network unit 702 may be converged first, before the start of the        booster normal operation.

The above discussion is applicable to all the different analogueimplementations of all the various disclosed boosters.

Digital Implementation Example

FIG. 9 shows an example of digital implementation of the Network unit602 (labeled 1002 in FIG. 9), which is placed where good signal coverageexists, indoor or outdoors. Two antennas 1004 and 1006 are used forantenna diversity for the cellular band transmitter and receiver of theNetwork unit 1002. Also two antennas 1036 and 1038 are used for antennadiversity of the U-NII band operation of the Network unit 1002. Althoughany diversity-combining scheme such as Maximal Ratio Combining or otherscan be used for the receiver chain and transmit diversity schemes suchas random phase change in one or both antennas may be used for thetransmitter chain, a simple scheme based on antenna switched diversityis disclosed. Switching may be continuous or based on received signalpower level. Therefore, RF switch 1008 may be connected to duplexers1007 and 1010 and Low Noise Amplifier (LNA) unit 1012 performs switchingoperations for the cellular receive operation of the Network unit 1002.Also, RF switch 1032 connected to antennas 1036 and 1038 and the duplexfilter 1034 performs switching operations for the U-NII bandtransmit/receive operation of the Network unit 1002. The duplex filters1007 and 1010 are also connected to antennas 1004 and 1006 on one sideand to the Complex-Weight unit 1072 on the other side, as well as RFswitch unit 1008. The complex-weight unit 1072 is connected topower-splitter hybrid combiner 1070 and the micro-controller 1060. Thepower-splitter hybrid combiner 1070 is connected to power amplifier unit1054 via the directional coupler 1056. All directional couplers may be17 dB directional couplers. Low Noise Amplifier (LNA) 1012 is connectedto the frequency converter unit 1014. Frequency converter 1014 isconnected to Automatic Gain Control (AGC) unit 1018. The frequencyconverter 1014 converts the frequency band of the incoming signal fromthe cellular band to baseband, or “near baseband” frequency band. Thefrequency converter unit 1014 includes all filtering for correctoperation of the receiver chain. The operating frequency of thefrequency converter unit 1014 is set by micro-controller unit 1060. TheAGC unit 1018 is connected to Analogue to Digital Converter (ADC) unit1020 and the Signal Conditioning (SC) unit 1022. The AGC 1018 isoptional and places the received signal level substantially close to themiddle of the dynamic range of the ADC 1020. If included, AGC 1018 isconfigured so that in the presence of low signal power, noise within theoperating bandwidth does not dominate the operation of the AGC unit1018. AGC 1018 is also configured so that the gain contribution of theAGC unit 1018 is compensated in the final Down-link System Link GainG_(dl) calculations or the gain value of the AGC 1018 is compensated inthe Signal Conditioning (SC) unit 1022. If AGC unit 1018 is used inNetwork unit 1002 and the unit is designed for Code Division MultipleAccess (CDMA) cellular networks, AGC bandwidth is selected to be muchsmaller than the power control repetition rate of the CDMA system, forexample less than 1.5 kHz in WCDMA networks, so that the AGC operationdoes not interfere with the closed-loop power control. If AGC unit 1018is not included, the ADC unit 1020 is designed to supply sufficientdynamic range, which can be as high as 192 dB (32-bits). The ADC unit1020 is connected to the Signal Conditioning unit 1022. The SignalConditioning unit 1022 performs tasks including channel select filteringfor the selected operating frequency band, frequency conversion,insertion of reference frequency, signal level estimation, an AGCalgorithm, WLAN transmitter algorithms, and other signal conditioningand processing features. For example, channel select filters that can beimplemented as poly-phased filters and set for a selected operatingbandwidth of 1.3, 5, 10 or 15 MHz, operating at any position within theforward-link cellular or Personal Communication Services (PCS) orselected frequency spectrum. Signal Conditioning unit 1022 clockfrequency is derived from a local reference frequency unit 1070 andprovided by clock unit 1024. Depending on system parameters, operationalbandwidth, and load of the supported operations such as filtering, theSignal Conditioning unit 1022 may be implemented by a variety oftechnologies such as field-programmable gate arrays (FPGAs),application-specific integrated circuits (ASICs), and general purposedigital signal processors (DSPs) such as Texas InstrumentsTMS320C6416-7E3 processor. The Signal Conditioning unit 1022 includesall appropriate interfaces and memory. The Signal Conditioning unit 1022is connected to Digital to Analogue Converter (DA/C) unit 1026. The DA/Cunit 1026 includes sufficient post filtering after digital to analogueconversion. The DA/C unit 1026 is connected to frequency converter unit1028. Frequency converter unit 1028 up-converts the frequencies of theinput signal to the selected portion of U-NII band of frequencies. Thefrequency converter unit 1028 includes sufficient filtering for correctoperation of the transmitter chain. The operating frequency of thefrequency converter unit 1028 is set by micro-controller unit 1060.Therefore, a Dynamic Channel Allocation (DCA) algorithm can be used toselect the best operating frequency band. The frequency converter unit1028 is connected to the variable gain amplifier unit 1030. Gain ofamplifier 1030 is set by the micro-controller unit 1060 and may be setto the maximum allowed power for transmission in U-NII band. Thevariable gain amplifier unit 1030 is connected to Duplex filter 1034.The duplex filter 1034 is connected to reverse-link LNA 1040 and the VGamplifier 1030. LNA 1040 is connected to the frequency converter unit1042. Frequency converter unit 1042 is connected to the directionalcoupler unit 1041. The frequency converter 1042 converts the frequencyband of the incoming signal from the U-NII band to baseband, or “nearbaseband” frequency band. The frequency converter unit 1042 includesappropriate filtering for correct operation of the receiver chain. Theoperating frequency of the frequency converter unit 1042 is set bymicro-controller unit 1060. Directional coupler unit 1041 is connectedto Automatic Gain Control (AGC) unit 1044 and the calibration signalreceiver unit 1016. The AGC unit 1044 is connected to Analogue toDigital Converter (AD/C) unit 1046 and the Signal Conditioning unit1048. The AGC 1044 is optional and is used to place the received signallevel substantially close to the middle of the dynamic range of the AD/C1046. If included, AGC 1044 is implemented so that in the presence oflow signal power, noise within the operating bandwidth does not dominatethe operation of the AGC unit 1044. Gain contribution of the AGC unit1044 is selected to compensated in the final Up-link System Link GainG_(ul) calculations, or the gain value of the AGC 1044 is compensated inthe Signal Conditioning (SC) unit 1048. If AGC unit 1044 is used inNetwork unit 1002 and the unit is designed for CDMA cellular networks,AGC bandwidth is selected to be much smaller than the power controlrepetition rate of the CDMA system, for example less than 1.5 kHz inWCDMA networks, so that AGC operation does not interfere with theclosed-loop power control mechanism. If the AGC unit 1044 is notincluded, the AD/C unit 1046 is configured to supply suitable dynamicrange, which can be as high as 192 dB (32-bits). The AD/C unit 1046 isconnected to the Signal Conditioning unit 1048. The Signal Conditioningunit 104& performs tasks including channel select filtering for theselected operating frequency band, frequency conversion, signalcalibration receiver, signal level estimation, AGC algorithm, WLANreceiver algorithms and any other features that use signal conditioningand processing. For example, the channel select filters that can beimplemented as poly-phased filters and set for a selected operatingbandwidth of 1.3, 5, 10 or 15 MHz, operating at any position within theforward-link U-NII or a selected frequency spectrum. The SignalConditioning unit 1048 clock frequency may be derived from a localreference frequency unit 1070 and supplied by clock unit 1024. Dependingon the system parameters such as operational bandwidth and supportedoperation load such as filtering, the Signal Conditioning unit 1048 maybe implemented by a variety of technologies such as Field ProgrammableGate Arrays (FPGAs), Application-Specific Integrated Circuits (ASICs)and general purpose Digital Signal Processors (DSPs) such as TexasInstruments TMS320C6416-7E3 processor. The Signal Conditioning unit 1048includes appropriate interfaces and memory. The Signal Conditioning unit1048 is connected to Digital to Analogue Converter (DA/C) unit 1050. TheDA/C unit 1050 is connected to frequency converter unit 1052. The DA/Cunit 1050 implements suitable post filtering following digital toanalogue conversion. Frequency converter unit 1052 up-converts thefrequencies of the input signal to the selected portion of cellular orPersonal Communication Services (PCS) band of frequencies. The frequencyconverter unit 1052 includes appropriate filtering for correct operationof the transmitter chain. The operating frequency of the frequencyconverter unit 1052 is set by micro-controller unit 1060. The frequencyconverter unit 1052 is connected to the power amplifier unit 1054. Thepower amplifier unit 1054 is connected to directional coupler 1056.

A calibration signal generator/transmitter unit 1058 is coupled to thereverse-link transmitter path of the Network unit 1002 via thedirectional coupler 1056. The unit 1058 generates a channel-soundingsignal, which is used to establish the complex channel characteristicsbetween the Network unit 1002 antennas 1004 and 1006 and the inputterminal to the calibration signal receiver 1016. The channel-soundingsignal generated by unit 1058 is transmitted via the complex-weight unit1072 and the diversity antennas 1004 and 1006 with a maximum transmitlevel, which is substantially below any expected signal level fromcellular network, for example 20 dB below the minimum expected cellularsignal level. The combined transmitted channel-sounding signal level andthe processing gain used in the calibration signal receiver unit 1016 isless than or equal to the Up-link Gain Margin dg_(ul). Thechannel-sounding signal generated by unit 1058 is a direct-sequencespread spectrum signal modulated by a known Pseudo Random (PN) code witha known code phase, called an “own code” phase, and having a chippingrate comparable to the forward and reverse links of the Network unit1002 and User unit 2002 shown in FIG. 10 operating bandwidths, forexample 5 Mchips/s for 5 MHz bandwidth, and a minimum code length tosupply a suitable processing gain. The code length is supplied which islonger than the maximum expected path delay. A code length of 1000 chipsis adequate for most scenarios. The channel-sounding signal can betransmitted continuously or transmitted only when prompted bytransmission. The code phases are selected such that the minimum codephase difference is larger than the maximum expected path delay measuredin a multiple number of chips. Subsequent code phases are integermultiples of the minimum code phase. The calibration signal receiverunit 1016 is coupled to the reverse-link receive path of the Networkunit 1002 by directional coupler 1041 using the known PN code. Thetransmit code phase is capable of detecting and demodulating thechannel-sounding signal transmitted by unit 1058, which enters thereverse-link path via the closed-loop existing between the Network unit1002 and the User unit 2002 in FIG. 10. The calibration signal receiverunit 1016 is adapted to establish the received signal strength andphase. A complex channel impulse response exists between the Networkunit 1002 combined outputs of antennas 1004 and 1006 and the inputterminal to the calibration signal receiver 1016. The calibration signalreceiver unit 1016 establishes the signal either by a correlationoperation similar to a RAKE receiver path searcher or by matrixinversion operation on an appropriate block of sampled received signal.The calibration signal receiver unit 1016 includes many sub-units, forexample a frequency converter, to return the calibration signal tobase-band frequencies. Other sub-units are A/D converters and base-bandprocessors to perform base-band algorithms. The PN code phase can beassigned uniquely or determined according to a random algorithm so thatthe probability of two units having the same code phase can be very low.Other code offset assignment strategies are also possible, such asdynamic assignment in which a code offset is selected so long as noother signal with the same offset is detected in that geographical area.Dynamic assignment enables the calibration signal receiver 1016 to beable to scan and receive “other code” phases, and hence establisheswhether any other signal coupling to or from other units exists that maybe operating in the same geographical area. More than one code phasescan be used to establish the complex channel impulse response so thatthe probability of detection by other systems is increased. The PN codeused for the channel-sounding signal can be modulated with informationabout the identity of the Network unit 1002. The carrier frequency ofthe transmitted channel-sounding signal may be the operating cellularfrequency band. In other embodiments, carrier frequencies in other bandsmay be used, such as ISM band at 2.4 GHz, for transmission of thechannel-sounding signal. In the other bands, the calibration signalgenerator and transmitter 1058 carrier frequency is placed as near aspossible to the operating frequency band. The chipping rate and thetransmit power of the channel-sounding signal PN code are implemented sothat the channel-sounding signal complies with the FCC 47 CFR Part-15rules. The ISM band, although not the same as the cellular operatingband, is sufficiently close to enable the system to converge the spatialalgorithm weights and establish the weights W₀ and W₁ used in thecomplex-weight unit 1072. Any antenna and propagation differences inaverage signal power and antenna behavior between the ISM and cellularoperating bands can be analyzed and minimized by selection of filteringparameters.

The calibration transmitter unit 1058 and the calibration receiver unit1016 baseband functions, as well as the complex-weight unit 1072 can beintegrated and supported by the Signal Conditioning unit 1048. In thisexample, the complex-weight unit 1072 is implemented in combination withtwo amplifiers such as amplifiers 1054 positioned before the duplexfilters 1007 and 1010. Also in the illustrative example, the calibrationsignal generator and transmitter unit 1058 and the calibration signalreceiver 1016 are both in the Network unit 1002. In other embodimentsone or more of the calibration signal generator 1016, the transmitterunit 1058, and the calibration signal receiver 1016 can also be placedin the User unit 2002 with various modifications and taking into accountdesign considerations. The Equipment ID and reference frequency unit 624shown in FIG. 6 in the forward-link path may be supported by the SignalConditioning unit 1022 in the digital Network unit 1002. The descriptionand function may be the same as for unit 624.

The control link unit 1062 may be a radio link between the two Networkunit 1002 and the User unit 2002 shown in FIG. 10. The control link 1062may be a proprietary link that operates in one of the unlicensed band offrequencies or may be a standard wireless link such as 802.11b, 802.11a,802.11g or Bluetooth links, designed to operate in the unlicensed band.The control link unit 1062 is connected to micro-controller unit 1060and is adapted to communicate with the Network or User unit through anappropriate interface. The control link unit 1062 is also connected toantennas 1066 and 1064 for transmission and reception of the controlsignals. Antenna bandwidth and operating frequency may enable, withminor modifications to unit 1002, antenna units 1036 and 1038 to performcontrol link unit 1062 operations. Minor modifications to unit 1002 andappropriate selection of operating frequencies enable basebandfunctionality of the control link unit 1062 to be included in the SignalConditioning units 1022 and 1048. Transmit/receive control link unit1062 signals may be multiplexed in frequency or time with thetransmit/receive signals of the forward and the reverse-link Networkunit 1002 that are transmitted and received by antennas 1038 and 1036.

Micro-controller unit 1060 may be a simple micro-processor such as ARM7or ARM9 with appropriate memory and interfaces. The micro-controllerunit 1060 may control operation of the Network unit 1002 and may performadditional signal conditioning and processing such as signal levelaveraging and estimation and adaptive algorithms such as LeastMean-Square (LMS) and Recursive Least Squares (RLS). Themicro-controller unit 1060 may also set the operating bandwidth andweights W₀ and W₁ to communicate and control the User unit 2002 via thecontrol link unit 1062 and to communicate and control the calibrationsignal generator and transmitter 1058 and calibration signal receiver1016 to operate switching for the receiver antenna diversity and monitorthe correct operation of the Network unit 1002 and User unit 2002. Othertasks of the micro-controller 1060 are disclosed in detail in thediscussion of FIGS. 7A, 7B, 7C, and 7D. The illustrativemicro-controller unit 1060 is connected to units 1062, 1016, 1058, 1052,1048, 1042, 1030, 1028, 1022, 1072 and 1014, as well as the RF switches1008 and 1032. The micro-controller 1060 uses the complex channelimpulse response at the output terminal of the calibration signalreceiver unit 1016 and may use Least Mean-Square (LMS), Recursive LeastSquares (RLS), QR-RLS, or QR decomposition to compute optimum values ofthe complex weights W₀ and W₁ such that the received complex channelimpulse response at the output terminal of the calibration signalreceiver unit 1016 is minimized or reduced. The determined transmitweights enable radio frequency (RF) isolation for up-link frequenciesbetween the Network unit 1002 and the User unit 2002 within thepropagation channel, and further may enable a maximum possible overallERP (Effective Radiated Power) from antennas 1004 and 1006, resulting ina maximum coverage footprint.

Units 1062, 1016, 1058, 1052, 1042, 1060, 1028, 1046, 1020, 1024 and1014 are depicted in an arrangement connected to local oscillator unit1070, or may otherwise derive clock and reference frequencies from thelocal oscillator 1070 signal. A simple user interface unit 1061, whichmay be a keypad, a simple dipswitch, or other device, may be connectedto micro-controller unit 1060. The Network unit 1002 has a unique“identity code”, which can be set by the user interface unit 1061, isaccessible to the micro-controller unit 1060, and can be communicated tothe User unit 2002 micro-controller unit 2054 or other User units thatmay be within operating range of Network unit 1002.

FIG. 10 shows an example of digital implementation of the User unit 702,for example labeled 2002 in FIG. 10, which may be positioned in alocation with poor signal coverage, either indoor or outdoors. Twoantennas 2034 and 2036 may be used for antenna diversity for thecellular band transmitter and receiver of the User unit 2002. Twoantennas 2004 and 2006 may be used for antenna diversity of the U-NIIband operation of the User unit 2002. Although, any diversity-combiningscheme such as Maximal Ratio Combining or others may be used for thereceiver chain and for transmit diversity schemes such as random phasechange in one or both antennas for the transmitter chain, a simplescheme that is based on antenna switched diversity may also be used.Switching may be continuous or based on received signal power level.Therefore, the RF switch 2032 connected to duplexers 2030 and 2031 andthe Low Noise Amplifier (LNA) unit 2038 performs switching operationsfor cellular receive operation of the User unit 2002. RF switch 2008connected to antennas 2004 and 2006 and the duplex filter 2010 performsswitching operations for the U-NII band transmit/receive operation ofthe User unit 2002. Duplex filters 2030 and 2031 are also connected toantennas 2036 and 2034 on one side and to the Complex-Weight unit 2072on the other side, as well as the RF switch unit 2032. Thecomplex-weight unit 2072 is connected to power-splitter hybrid combiner2070 and the micro-controller 2054. The power-splitter hybrid combiner2070 is connected to power amplifier unit 2028 via the directionalcoupler 2027. The directional couplers may be 17 dB directionalcouplers. Low Noise Amplifier (LNA) 2038 is connected to the frequencyconverter unit 2040. Frequency converter 2040 is connected to AutomaticGain Control (AGC) unit 2042. The frequency converter 2040 converts thefrequency band of the incoming signal from the cellular band to basebandor to a “near baseband” frequency band. Frequency converter unit 2040performs appropriate filtering for correct operation of the receiverchain. The operating frequency of the frequency converter unit 2040 isset by micro-controller unit 2054. Automatic Gain Control (AGC) unit2042 is connected to Analogue to Digital Converter (AD/C) unit 2044 andthe Signal Conditioning (SC) unit 2046. AGC 2042 is optional and is usedto set the received signal level substantially close to the middle ofthe dynamic range of the AD/C 2044. If included, AGC 2042 is adapted sothat in the presence of low signal power, noise within the operatingbandwidth does not dominate and the gain contribution is compensated inthe final Up-link System Link Gain G_(ul) calculations. Otherwise, thegain value of the AGC 2042 is compensated in Signal Conditioning (SC)unit 2046. If AGC unit 2042 is used in the User unit 2002 and the unitis designed for CDMA cellular networks, AGC bandwidth is selected to bemuch smaller than the power control repetition rate of the CDMA system,for example less than 1.5 kHz in WCDMA networks, so that AGC operationdoes not interfere with closed-loop power control. If AGC unit 2042 isnot included, the AD/C unit 2044 supplies a suitable dynamic range,which can be as high as 192 dB (32-bits). The AD/C unit 2044 isconnected to the Signal Conditioning unit 2046.

Signal Conditioning (SC) unit 2046 performs tasks includingchannel-select filtering for the selected operating frequency band,frequency conversion, insertion of reference frequency, signal levelestimation, AGC algorithm, WLAN transmitter algorithms, and other signalconditioning and processing features. For example, channel selectfilters that can be implemented as poly-phased filters and set for aselected operating bandwidth of 1.3, 5, 10 or 15 MHz, operating at anyposition within the forward-link cellular or Personal CommunicationServices (PCS) or the selected frequency spectrum. The SignalConditioning unit 2046 clock frequency is derived from a local referencefrequency unit 2023 and supplied by clock unit 2022. Depending on thesystem parameters and operational bandwidth and the load of thesupported operations such as filtering, the Signal Conditioning unit2046 may be implemented by a variety of technologies such asField-Programmable Gate Arrays (FPGAs), Application-Specific IntegratedCircuits (ASICs), and general purpose Digital Signal Processors (DSPs)such as Texas Instruments TMS320C6416-7E3 processor. The SignalConditioning unit 2046 includes appropriate interfaces and memory. TheSignal Conditioning unit 2046 is connected to Digital to AnalogueConverter (DA/C) unit 2048. The DA/C unit 2048 includes post filteringthat is appropriate after digital to analogue conversion. The DA/C unit2048 is connected to frequency converter unit 2050. Frequency converterunit 2050 up-converts frequencies of the input signal to the selectedportion of U-NII band of frequencies. The frequency converter unit 2050includes appropriate filtering for correct operation of the transmitterchain. Operating frequency of the frequency converter unit 2050 is setby micro-controller unit 2054. Dynamic Channel Allocation (DCA) may beused to select the best operating frequency band. The frequencyconverter unit 2050 is connected to the variable gain amplifier unit2052. The gain of this amplifier 2052 is set by the micro-controllerunit 2054 and can be set to maximum allowed power for transmission inU-NII band. The variable gain amplifier unit 2052 is connected to Duplexfilter 2010. The duplex filter 2010 is connected to forward-link LNA2012 and the VG amplifier 2052. Low Noise Amplifier (LNA) 2012 isconnected to the frequency converter unit 2014. Frequency converter unit2014 is connected to the directional coupler unit 2017. The frequencyconverter 2014 converts the frequency band of the incoming signal fromthe U-NII band to baseband or a “near baseband” frequency band. Thefrequency converter unit 2014 includes filtering for correct operationof the receiver chain. Operating frequency of the frequency converterunit 2014 is set by micro-controller unit 2054. Directional coupler unit2017 is connected to Automatic Gain Control (AGC) unit 2016 and thecalibration signal receiver unit 2015. The AGC unit 2016 is connected toAnalogue to Digital Converter (AD/C) unit 2018 and the SignalConditioning unit 2020. The AGC 2016 is optional and sets receivedsignal level substantially close to the middle of the dynamic range ofthe AD/C 2018. If included, AGC 2016 is configured so that in thepresence of low signal power noise within the operating bandwidth doesnot dominate operation and gain contribution is compensated in the finalDown-ink System Link Gain G_(dl) calculations. Otherwise, the gain valueof AGC 2016 is compensated in the Signal Conditioning (SC) unit 2020. IfAGC unit 2016 is used in the User unit 2002 and the unit is designed forCode Division Multiple Access (CDMA) cellular networks, AGC bandwidth isselected to be much smaller than the power control repetition rate ofthe CDMA system, for example less than 1.5 kHz in WCDMA networks, sothat AGC operation does not interfere with the closed-loop powercontrol. If AGC unit 2016 is not included, AD/C unit 2018 supplies asuitable dynamic range, which can be as high as 192 dB (32-bits). AD/Cunit 2018 is connected to Signal Conditioning unit 2020. SignalConditioning unit 2020 performs tasks including channel select filteringfor the selected operating frequency band, frequency conversion, signalcalibration receiver, signal level estimation, AGC algorithm, WLANreceiver algorithms, and other signal conditioning and processingfeatures. For example, channel select filters may be implemented aspoly-phased filters and set for a given operating bandwidth of 1.3, 5,10 or 15 MHz, operating at any position within the forward-link U-NII ora selected frequency spectrum. The Signal Conditioning unit 2020 clockfrequency is derived from clock unit 2022 with the reference frequencysupplied by unit 2023. Depending on the system parameters such asoperational bandwidth and supported operation load such as filtering,the Signal Conditioning unit 2020 may be implemented by a variety oftechnologies such as Field-Programmable Gate Arrays (FPGAs),Application-Specific Integrated Circuits (ASICs), and general purposeDigital Signal Processors (DSPs) such as Texas InstrumentsTMS320C6416-7E3 processor. The Signal Conditioning unit 2020 includesappropriate interfaces and memory. The Signal Conditioning unit 2020 isconnected to Digital to Analogue Converter (DA/C) unit 2024. The DA/Cunit 2024 is connected to frequency converter unit 2026. The DA/C unit2024 includes post filtering that is appropriate after digital toanalogue conversion. Frequency converter unit 2026 up-converts thefrequencies of the input signal to the selected portion of cellular orPersonal Communication Services (PCS) band of frequencies. The frequencyconverter unit 2026 includes filtering for correct operation of thetransmitter chain. The operating frequency of the frequency converterunit 2026 is set by micro-controller unit 2054. The frequency converterunit 2026 is connected to the power amplifier unit 2028. The poweramplifier unit 2028 is connected to directional coupler 2027.

A calibration signal generator/transmitter unit 2025 is coupled to theforward-link transmitter path of the User unit 2002 via directionalcoupler 2027 and generates a channel-sounding signal, which isestablishes the complex channel characteristics between the User unit2002 antennas 2034, 2036 and the input terminal to the calibrationsignal receiver 2015. The channel-sounding signal generated by unit 2025is transmitted via the complex-weight unit 2072 and the diversityantennas 2034 and 2036 with a maximum transmit level substantially belowany expected signal level from cellular network, for instance 20 dBbelow the minimum expected cellular signal level. The combinedtransmitted channel-sounding signal level and the processing gain usedin the calibration signal receiver unit 2015 is less than or equal tothe Down-link Gain Margin dg_(dl). The channel-sounding signal generatedby unit 2025 is a direct-sequence spread spectrum signal modulated by aknown Pseudo Random (PN) code with a known code phase, which may betermed an “own code” phase. The channel-sounding signal has a chippingrate comparable to the forward and reverse links of the User unit 2002and Network unit 1002 in FIG. 9 operating bandwidths, for example 5Mchips/s for 5 MHz bandwidth, and a minimum code length to supply asuitable processing gain. The channel-sounding signal is generated witha time code length longer than the maximum expected path delay. A codelength of 1000 chips is adequate for most scenarios. Thechannel-sounding signal can be transmitted continuously or transmittedonly when prompted by transmission. Code phases are selected such thatthe minimum code phase difference is larger than the maximum expectedpath delay, measured in multiple number of chips. Subsequent code phasesare integer multiples of the minimum code phase. The calibration signalreceiver unit 2015 is coupled to the forward-link receive path of theUser unit 2002 by directional coupler 2017 using the known PN code. Thetransmit code phase is capable of detecting and demodulating thechannel-sounding signal transmitted by unit 2025, which enters thereverse-link path via the closed-loop mechanism that exists between theUser unit 2002 and the Network unit 1002. The calibration signalreceiver unit 2015 is adapted to establish the received signal strengthand phase, either by correlation operation similar to a RAKE receiverpath searcher or by matrix inversion operation on an appropriate blockof sampled received signal. A complex channel impulse response existsbetween the User unit 2002 combined outputs of antennas 2034, 2036 andthe input terminal to the calibration signal receiver 2015.

The calibration signal receiver unit 2015 includes many sub-units. Afrequency converter sub-unit returns the calibration signal to base-bandfrequencies. Other units such as A/D converters and base-band processorsperform base-band algorithms. The PN code phase can be assigned uniquelyor determined according to a random algorithm whereby the probability oftwo units having the same code phase can be very low. Other code offsetassignment strategies may otherwise be used, such as dynamic assignment,whereby a code offset is selected so long as the offset is not otherwisedetected in the geographical area. Offset determination enables thecalibration signal receiver 2015 to scan and receive “other code”phases, establishing whether any other signal couples to other unitsthat may be operating in the same geographical area. More than one codephase can be used to establish the complex channel impulse response sothat the probability of detection by other systems is increased. The PNcode for the channel-sounding signal can be modulated with informationabout the identity of the User unit 2002. The carrier frequency of thetransmitted channel-sounding signal may be set to the operating cellularfrequency band or may be set to carrier frequencies in other bands, suchas ISM band at 2.4 GHz, for transmission of the channel-sounding signal.For operating frequencies outside the cellular band, the calibrationsignal generator and transmitter 2025 carrier frequency is placed asnear as possible to the operating frequency band. The chipping rate andthe transmit power of the channel-sounding signal PN code areimplemented so that the channel-sounding signal complies with the FCC 47CFR Part-15 rules. The ISM band, although not the same as the cellularoperating band, is sufficiently close to enable the system to convergethe spatial algorithm weights, and establish the weights W₀ and W₁ usedin the complex-weight unit 2072. Any antenna and propagation differencesin average signal power and antenna behavior between the ISM andcellular operating bands can be taken into account in filterimplementation.

The calibration transmitter unit 2025 and the calibration receiver unit2015 baseband functions, as well as the complex-weight unit 2072 may beintegrated and supported by the Signal Conditioning unit 2020. In theillustrative example, two amplifiers 2028 are positioned before duplexfilters 2031 and 2030. The depicted example also includes thecalibration signal generator and transmitter unit 2025 and thecalibration signal receiver 2015, are contained both within the Userunit 2002. In other embodiments, in one or both of the Network and Userunits, calibration signal generator and transmitter unit 2025, and thecalibration signal receiver 2015 may also be placed in the Network unit1002 with some modifications. The reference frequency receiver unit 716shown in FIG. 7 in the forward-link path and may be supported by theSignal Conditioning unit 2020 in the digital User unit 2002 with similarstructure and function to unit 716.

Control Link unit 2056 may be a radio link between the Network unit 1002and the User unit 2002, may be a proprietary link that operates in oneof the unlicensed band of frequencies, or may be a standard wirelesslink such as 802.11b, 802.11a or Bluetooth designed to operate inunlicensed band. The control link unit 2056 is connected tomicro-controller unit 2054 and may be adapted to communicate with theunit through an appropriate interface. The control link unit 2056 mayalso connected to antennas 2058 and 2060 for transmission and receptionof the control signals. At suitable antenna bandwidth and operatingfrequency, antenna units 2004 and 2006 can also be used for control linkunit operations with minor modifications to unit 2002. Also, with minormodifications to unit 2002 and with suitable selected operatingfrequencies, baseband functionality of the control link unit 2056 can beincluded in the Signal Conditioning units 2046 and 2020 withtransmit/receive control link unit 2056 signals multiplexed in frequencyor time. Transmit/receive signals of the forward and reverse User unit2002 are transmitted and received by antennas 2004 and 2006.

Micro-controller unit 2054 may be a simple micro-processor such as ARM7or ARM9 with appropriate memory and interfaces. Micro-controller unit2054 controls operation of the User unit 2002 and may perform someadditional signal conditioning and processing operations such as signallevel averaging and estimation and adaptive algorithms. Suitableadaptive algorithms include Least Mean-Square (LMS) and Recursive LeastSquares (RLS). Micro-controller unit 2054 sets the operating bandwidthand sets weights W₀ and W₁ to communicate and control the Network unit1002 in FIG. 9 via the control link unit 2056, communicate and controlthe calibration signal generator and transmitter 2025 and calibrationsignal receiver 2015, operate switching for the receiver antennadiversity, and monitor for correct operation of the User unit 2002.Other micro-controller 2054 operation examples are discussed withreference to FIGS. 7A, 7B, 7C, and 7D. Micro-controller unit 2054 isconnected to units 2056, 2052, 2050, 2046, 2040, 2026, 2020, 2015, 2025,2072 and 2014, as well as the RF switches 2032 and 2008.Micro-controller 2054, using the complex channel impulse response at theoutput of the calibration signal receiver unit 2015, and using LeastMean-Square (LMS), Recursive Least Squares (RLS), QR-RLS, or QRdecomposition computes the optimum values of the complex weights W₀ andW₁ such that the received complex channel impulse response at the outputof the calibration signal receiver unit 2015 is minimized or reduced.With the transmit weights arrangement, radio frequency (RF) isolationfor down-link frequencies between the User unit 2002 and the Networkunit 1002 is adapted within the propagation channel, enabling themaximum possible overall ERP (Effective Radiated Power) from antennas2034 and 2036 and generating the maximum coverage footprint.

Units 2056, 2050, 2040, 2026, 2054, 2018, 2044, 2022, 2025, 2015 and2014 are connected to local oscillator unit 2023 or derive clock andreference frequencies from the local oscillator 2023 signal. A simpleuser interface unit 2055, which can be a keypad, a simple dipswitch, orsimilar device, is connected to micro-controller unit 2054. The Userunit 2002 has a unique “identity code”, which can be set by the userinterface unit 2055 and is accessible to the micro-controller unit 2054,and can be communicated to the Network unit 1002 micro-controller unit1060.

The control-flow description given for FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C,and 8D may also be used for the digital implementation of the Networkunit 1002 and User unit 2002, and is discussed with respect to FIGS. 9and 10.

In the reverse-link operation of the Network unit 1002 and the User unit2002, for example, signals received through antenna units 2034 and 2036are re-transmitted through the antenna units 1004 and 1006 at a highersignal power. The re-transmitted signals can be received again throughthe antenna units 2034 and 2036 and may be termed “Up-linkReturned-Signals”, causing a signal return path that may causeinstability in booster operation. In the digital implementation ofNetwork unit 1002 and User unit 2002, magnitude of the returned “Up-linkReturned-Signal” may be reduced by various signal-processing techniques.

The selection, design, and effectiveness of a technique depend on systemparameters and operating conditions. Most multi-path mitigationalgorithms may be applied for return signal reduction. However, due tothe extremely small propagation delays between the Network unit 1002 andthe User unit 2002 and limited system temporal resolution, conventionalalgorithms may be, at best, difficult and expensive to implement inpractice and, at worst, detrimental. Accordingly, an example of a novelfiltering technique is described in the “Novel Channel Filtering”section. A deliberate delay is inserted in re-transmission of thereceived signal to separate the returned signal (“Up-linkReturned-Signal”) from the original incident signal at the outputterminators of the antenna unit 2034 and 2036. For example, a delay ofabout μsec ensures time separation of the re-transmitted signal from theoriginal received signal, and enables mitigation of the re-transmittedsignal by using a “Channel Filtering” technique. Delay can be introducedin the Signal Conditioning unit 1048 given availability of a digitaldata buffer of sufficient size. The Channel Filtering operation can beperformed by the Signal Conditioning unit 1048 or Signal Conditioningunit 2046, or can be performed by a separate ASIC or FPGA connected tothe AD/C unit 1046 and the Signal Conditioning unit 1048. In anotherembodiment, with minor modifications the “channel filtering” ASIC orFPGA unit can be placed in the User unit 2002, connected to the AD/Cunit 2044 and Signal Conditioning unit 2046. The channel-sounding signalcan be used for channel estimation, so that amplitude and the phase ofthe overall channel response including the return path can be estimatedduring the channel-sounding mode following convergence of thecomplex-weight unit 1072 weights W₀ and W₁ for setting the ChannelFilter taps. Introduction of Channel Filter in the signal path also hasan impact on the operation of the antenna diversity scheme. Duringperformance of the complex channel estimation, antenna switchingoperations are synchronized so that of possible switched antennacombinations, only two possibilities exist. Antenna switching orselection may be controlled by micro-controller unit 1060 in the Networkunit 1002 and micro-controller 2054 in the User unit 2002. Channelestimation can be performed for two propagation paths and two sets ofChannel Filter coefficients can be determined for filtering operation.Accordingly, relevant filter coefficients may be selected or switchedinto operation in synchrony and in harmony with antenna selection.Channel Filtering is not used to totally mitigate the returned signalbut rather is used to sufficiently suppress the signal so that somesystem gain is possible for the signal boosting operation. Introductionof the deliberate delay may also be used in conjunction with other knownsignal-processing algorithms to reduce coupling between the two Network1002 and User 2002 units. Similar analysis applies to the forward-linkof the Network unit 1002 and the User unit 2002. Accordingly, the“delay” and “Channel Filtering”, with aid of the forward-linkcalibration signal shown in FIG. 10, is performed in the forward-link ofthe User unit 2002.

Other techniques, such as use of vertical polarization for antenna units1004, 1006 and horizontal polarization for antennas 2034, 2036 canfurther improve the system performance. System performance may also beimproved by use of directional antennas.

The control-flow description given for FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C,and 8D may be modified for inclusion of the “Channel filtering” channelestimation in the digital implementation of the Network unit 1002 andUser unit 2002.

The illustrative description is only an example of how the system may beimplemented, and is not the only possible method and solution. Severalpoints are noted, as follows:

-   -   1. Network unit 1002 may control several User units, such as the        User unit 2002. In such configurations, the example control flow        shown in FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C, and 8D may be        implemented such that the Network Unit 1002 can initialize each        User unit independently at first, and in combination in a final        step. In a scenario with several User units such as 2002,        Network unit 1002 may converge weights for the User unit that        have minimum Up-link System Path Loss PL_(ul) with the Network        unit 1002. Therefore each User unit 2002 in a booster network        may have a unique code phase.    -   2. Another modification that is used for multiple-User unit        operation is that the final weights convergence of the units in        a booster network with Network and User units is performed with        all User units under control of the Network unit that is active        in the channel-sounding operation such that combined signal        power levels do not exceed the safe limit. If the combined        signal from the User Units exceeds the acceptable level for        either the reverse or forward system links, appropriate weights        are modified in iterative step increments to a level so that        maximum system link gains of the forward and the reverse links        are met.    -   3. Although the signal path in both the Network unit 1002 and        the User unit 2002 are typically always active in the forward        link direction to boost the beacon, for example the Broadcast        Control Channel (BCCH) in Global System for Mobile        Communications (GSM)) transmissions of the base stations. The        reverse-link signal path of the Network unit 1002 and the User        unit 2002 need not to be active unless a substantial signal        level is detected based on the presence of uplink, “gated”        signal. The reverse-link “gated” operation is managed to avoid        interference with the channel-sounding signal path and technique        involving the units 1058 and 1016. The “gated” operation becomes        a continuous operation during the channel-sounding process with        channel sounding performed on a regular basis.    -   4. Modifications in the hardware and the control software may be        implemented to merge the Network unit 1002 and the User unit        2002 into a single unit, connected “back-to-back”. The design        and operation of the back-to-back option is shown and disclosed        with reference to FIG. 12.    -   5. The unique Network unit 1002 identity code and optionally        device location may be transmitted to the cellular network. The        information can be used to locate a user in an indoor        environment by generating heavily-coded, protected, low bit rate        data that contains a long known preamble. The unique identity        code and optionally longitude and latitude of the Network unit        1002 may also be transmitted. The information can be        pulse-shaped for low spectral leakage and superimposed on the        reverse-link signal of a given channel by an appropriate        modulation scheme within the Network unit 1002. The modulation        scheme is selected based on the operating cellular system. For        example, GSM has a constant envelope modulation such as Gaussian        Minimum Shift Keying (GMSK) so that amplitude modulation with        low modulation index can be used. For CDMA systems with fast        reverse-link power control, Differential Binary Phase Shift        Keying (DBPSK) can be used as a modulation scheme. Extraction of        the information from the received channel signal at base station        involves base station receiver modifications but does not affect        the normal operation of the cellular link.    -   6. A closed-loop power control capability may also be        implemented between the Network unit 1002 and User unit 2002 for        the unlicensed band (U-NII) operation both in forward and        reverse links. Closed-loop power control can be based on very        low-rate, for example 10 Hz, differential or absolute power        control commands based on received signal power to increase or        reduce U-NII band transmission power. Closed-loop power control        limits power transmitted from the antennas 1036, 1038 on the        Network unit 1002 side and antennas 2004, 2006 on the User unit        2002 side to a minimum level sufficient for correct operation.        Variable gain amplifiers may be used for the transmission of the        U-NII band both in the Network unit 1002 and the User unit 2002.        The closed-loop power control messages can be exchanged between        the Network unit 1002 and the User unit 2002 via the control        link units 1062 and 2056 in forward and reverse-links.    -   7. On the Network unit 1002 side, once the complex-weight unit        1072 weights W₀ and W₁ are converged, spatial dither may be        superimposed on the antenna radiation pattern so that the        multipath standing waves patterns are sufficiently disturbed to        provide some diversity gain on the Up-link. A second set of        weights may also be converted that maintain spatial position of        “nulls” while changing the radiation pattern sufficiently to        create antenna radiation pattern diversity. Weights can be        converged by first performing direction finding, for example        using a discrete Fourier transform, on the original weights to        identify the ‘Null” position and forming new weights using        algorithms such as Minimum-Variance Linear-Constraint        Beam-forming algorithms (MVLCBF) with the constraint being the        position of the spatial “Null”. Repeated switching between the        two sets of weights performs antenna pattern diversity gain on        the up-link. A similar operation is applicable to the User unit        2002 for Down-link path.    -   8. In the example of the Network unit 1002 and the User unit        2002, only two sets of complex weights W₀ and W₁ are used in the        complex-weight units 1072 and 2072 since two diversity antennas        are readily available at both units. However, both in the        Network unit 1002 and in the User unit 2002 more than two        antennas and hence more than two weights can be used, based on        similar analysis with minor modifications.    -   9. Although the complex-weight units 1072 and 2072 in the        Network units 1002 and 2002, respectively, are used for        transmitter beam-forming, similar complex weight units may be        used at the input terminal of receivers of the forward-link of        the Network units 1002 and 2002 in place of RF switches 1008 and        2032 respectively, so that receiver beam-forming can also be        performed. The receiver weight convergence can be based on a        procedure similar to that of the transmitter with only minor        changes.    -   10. Weights W₀ and W₁ of the complex-weight units 1072 and 2072        in the Network units 1002 and 2002, respectively, may be        converged with the reverse-link of the Network unit 1002 not        operational, for example not receiving and transmitting the        up-link cellular band signals within the Signal Conditioning        unit 1048, and the forward-link of the User unit 2002 not        operational, for example not receiving and transmitting the        down-link cellular band signals within the Signal Conditioning        unit 2020, such that cellular signals are not repeated or        transmitted. The operation enables convergence of weights W₀ and        W₁ of the complex-weight units 1072 and 2072 in the Network        units 1002 and 2002 first, before the start of normal booster        operation.

The enumerated points are applicable to many different digital boosterimplementations.

Back-to-Back Booster

In a Back-to-Back arrangement, transmission and reception in U-NII bandand a control link between the Network unit 602 and the User unit 702may be eliminated. FIG. 11 depicts an analogue implementation example ofa suitable back-to-back arrangement. A booster can be positioned in alocation with good signal coverage, either indoors or outdoors. Theback-to-back unit 2252 includes antennas 2254, 2256, 2282 and 2280, alloperating in a cellular spectrum of interest. Antennas 2254 and 2256 areconnected to the duplex filters 2260 and 2259 respectively. The RFswitch 2258 is also connected to the duplex filters 2260 and 2259 toprovide antenna switched diversity operation for receive operation asdisclosed with respect to operation of Network unit 602 and User unit702. In the forward-link, Radio Frequency (RF) switch unit 2258 isconnected to the Low Noise Amplifier (LNA) 2288 in the Forward-link unit2264 via directional coupler 2261. The directional coupler unit 2261 mayalso be connected to calibration signal receiver unit 2263. Low NoiseAmplifier (LNA) 2288 is shown connected to the filter unit 2286.Bandpass filter unit 2286 can be designed to pass all or a desired partof the interested cellular spectrum or can be a bank of overlappingbandpass filters. Overlapping bandpass filters may cover the fullspectrum of interest in a cellular system with an RF switch included sothat the selected band and bandwidth can be selected either manually orautomatically. Filter unit 2286 is connected to the power amplifier2284. The power amplifier unit 2284 is connected to the directionalcoupler 2267. The directional coupler 2267 is connected to powersplitter unit hybrid combiner 2299 and to the calibration signalgenerator and transmitter unit 2265. Power splitter unit hybrid combiner2299 is connected to the complex-weight unit 2269. The complex-weightunit 2269 is connected to the duplex filters 2276 and 2277 and themicro-controller 2270. The duplex filters 2276 and 2277 are connected toantennas 2280 and 2282 and are connected to the RF switch 2278. On thereverse-link, the RF switch unit 2278 is connected to directionalcoupler unit 2274. The directional coupler unit 2274 is connected tocalibration signal receiver 2272 and Low Noise Amplifier (LNA) 2290 inthe Reverse-link unit 2266. Calibration signal receiver unit 2272 isadapted to establish the received signal strength and phase in a complexchannel impulse response that exists between the combined outputs ofantennas 2254, 2256 and the input terminal to the calibration signalreceiver 2272. Received signal strength and phase are established eitherby a correlation operation, which is similar to operation of a RAKEreceiver path searcher, or by a matrix inversion operation on anappropriate block of sampled received signal. The calibration signalreceiver unit 2272 may have many sub-units, including a frequencyconverter adapted to return the calibration signal to base-bandfrequencies, A/D converters, and base-band processors to performbase-band algorithms. Low Noise Amplifier (LNA) 2290 is connected tofilter unit 2292, which may in turn be connected to power amplifier unit2294. Bandpass filter 2292 can be designed to pass all or a desired partof the interested cellular spectrum, or can be a bank of overlappingbandpass filters, which cover the full spectrum of the cellular systemof interest. An RF switch may be included to manually or automaticallyselect band and bandwidth. Power amplifier 2294 is connected todirectional coupler unit 2262. Directional coupler unit 2262 isconnected to the calibration signal generator and transmitter unit 2268and power splitter unit, hybrid combiner 2296. Power splitter unit,hybrid combiner 2296 is connected to the complex-weight unit 2298. Thecomplex-weight unit 2298 is connected to the duplex filters 2260 and2259 and the micro-controller 2270. The duplex filters 2260 and 2259 areconnected to antennas 2254 and 2256 and connected to the RF switch 2258.The micro-controller 2270 is connected to calibration signal generatorand transmitter units 2268 and 2265, the calibration signal receiverunits 2272 and 2263, the Reverse-link unit 2266 and Forward-link unit2264. A simple user interface unit 2271, for example a keypad, simpledipswitch, or other switching unit, is connected to micro-controllerunit 2270.

Although many functional units of the Network unit 602 and the User unit702 are eliminated in the back-to-back unit 2252, operation and otherunits of the booster remain fundamentally the same as the componentsdescribed for the Network unit 602 and User unit 702. Operation anddescription of the calibration signal generator and transmitter units2268 and 2265, and the calibration signal receiver units 2272 and 2263in the reverse-link and forward-link are fundamentally similar to unitswith similar functionality described for the Network unit 602 and Userunit 702. Antenna units 2254, 2256, 2282 and 2280 are placed in mutualclose proximity, extra antenna isolation can be provided by highlydirectional antennas and an associated increase in front-to-backradiation ratios.

A unique unit 2252 identity code and optional device location may alsobe transmitted to the cellular network to supply information useful inlocating a user in an indoor environment. The information can betransmitted as heavily coded, protected, low bit-rate data, whichcontains a preamble, a unique identity code, and may optionally containthe longitude and the latitude of the unit 2252. The information can bepulse-shaped for low spectral leakage and superimposed on thereverse-link signal of a selected channel by an appropriate modulationscheme. The data handling may be performed within the unit 2252. Thechoice of the modulation scheme depends on the operating cellularsystem. For example, Global System for Mobile Communications (GSM) usesa constant envelope modulation such as Gaussian Minimum Shift Keying(GMSK) so that amplitude modulation with a low modulation index can beused. Code Division Multiple Access (CDMA) systems have fastreverse-link power control so that Differential Binary Phase ShiftKeying (DBPSK) can be used as the modulation scheme. Extraction ofinformation from the received channel signal at base station may usebase station receiver modifications, although the cellular linkmaintains normal operation.

FIG. 12 depicts a digital implementation example of a back-to-backarrangement with a booster is placed in a location with good signalcoverage, either indoors or outdoors. The back-to-back unit 2302includes antennas 2304, 2306,2328 and 2330, which operate in thecellular spectrum of interest. Antennas 2304 and 2306 are connected tothe duplex filters 2310 and 2309 respectively. RF switch 2308 is alsoconnected to the duplex filters 2310 and 2309 to perform an antennaswitched diversity operation for receive operation as discussed forNetwork unit 1002 and User unit 2002. In the forward-link, the RF switchunit 2308 is connected to the Low Noise Amplifier (LNA) 2312. Thedirectional coupler unit 2311 is connected to output of the LNA 2312 andthe calibration receiver unit 2305. The calibration receiver 2305 isalso connected to micro-controller 2350. The directional coupler unit2311 is also connected to the frequency converter unit 2313. Frequencyconverter 2313 is connected to Automatic Gain Control (AGC) unit 2314.The frequency converter 2313 converts the frequency band of the incomingsignal from the cellular band to baseband or “near baseband” frequencyband. The frequency converter unit 2313 includes filtering for correctoperation of the receiver chain. The operating frequency of thefrequency converter unit 2313 is set by micro-controller unit 2350. TheAGC unit 2314 is connected to Analogue-to-Digital Converter (AD/C) unit2316. The AGC 2314 is optional and sets received signal levelsubstantially close to the middle of the dynamic range of the AD/C 2316.If included, AGC 2314 is configured so that in the presence of lowsignal power noise within the operating bandwidth does not dominateoperation. The gain contribution of the AGC unit 2314 is compensated inthe final Down-link System Link Gain G_(dl) calculations. Otherwise, thegain value of the AGC 2314 may be compensated in the Signal Conditioningunit 2318. If AGC unit 2314 is used in the booster unit 2300 and thebooster unit is designed for Code Division Multiple Access (CDMA)cellular networks, AGC unit bandwidth is selected to be much smallerthan the power control repetition rate of the CDMA system, for exampleless than 1.5 kHz in WCDMA networks so that the AGC operation does notinterfere with the closed-loop power control. If AGC unit 2314 is notincluded, the AD/C unit 2316 may supply a suitable dynamic range whichcan be as high as 192 dB (32-bits). The AD/C unit 2316 is connected toSignal Conditioning unit 2318. The Signal Conditioning unit 2318performs such tasks as channel select filtering for the selectedoperating frequency band, frequency conversion, signal level estimation,AGC algorithm, and other signal conditioning and processing features.For example, channel select filters implemented as poly-phased filterscan be set for a given operating bandwidth of 1.3, 5, 10 or 15 MHzoperating at any position within the forward-link cellular or PersonalCommunication Services (PCS) or other selected frequency spectrum.Depending on the system parameters such as operational bandwidth andsupported operation load such as filtering, the Signal Conditioning unit2318 may be implemented by a variety of technologies such as FieldProgrammable Gate Arrays (FPGAs), Application-Specific IntegratedCircuits (ASICs) and general purpose Digital Signal Processors (DSPs)such as Texas Instruments TMS320C6416-7E3 processor. The SignalConditioning unit 2318 includes appropriate interfaces and memory and isconnected to Digital-to-Analogue Converter (DA/C) unit 2320. The DA/Cunit 2320 includes post filtering that is appropriate after digital toanalogue conversion. The DA/C unit 2320 is connected to frequencyconverter unit 2321. Frequency converter unit 2321 up-convertsfrequencies of the input signal to the original band of cellularfrequencies. The frequency converter unit 2321 includes appropriatefiltering for correct operation of the transmitter chain. The operatingfrequency of the frequency converter unit 2321 is set bymicro-controller unit 2350. The frequency converter unit 2321 isconnected to the power amplifier unit 2322, which is connected to thedirectional coupler unit 2325. The directional coupler unit 2325 isconnected to the calibration signal generator and transmitter unit 2323and the power splitter unit, hybrid combiner 2358. Power splitter unit,hybrid combiner 2358 is connected to the complex-weight unit 2360. Thecomplex-weight unit 2360 is connected to the duplex filters 2324 and2327 and the micro-controller 2350. The duplex filters 2324 and 2327 areconnected to antennas 2328 and 2330 and connected to the RF switch 2326.The calibration signal generator and transmitter unit 2323 is alsoconnected to the micro-controller 2350. On the reverse-link, the RFswitch unit 2326 is connected to micro-controller 2350 and alsoconnected to LNA unit 2332. The LNA unit 2332 is connected to thedirectional coupler unit 2334. The directional coupler unit 2334 isconnected to the frequency converter unit 2335. Frequency converter 2335is connected to Automatic Gain Control (AGC) unit 2336. The frequencyconverter 2335 converts the frequency band of the incoming signal fromthe cellular band to baseband or “near baseband” frequency band. Thefrequency converter unit 2335 includes filtering for correct operationof the receiver chain. The operating frequency of the frequencyconverter unit 2335 is set by micro-controller unit 2350. Thedirectional coupler unit 2334 is also connected to calibration signalreceiver unit 2348. The frequency converter unit 2335 is connected toAGC unit 2336. The AGC unit 2336 is connected to Analogue-to-DigitalConverter (AD/C) unit 2338. The AGC 2336 is optional and sets receivedsignal level substantially close to the middle of the dynamic range ofthe AD/C 2338. If included, AGC 2336 is configured so that in thepresence of low signal power, noise within the operating bandwidth doesnot dominate the operation of the AGC unit 2336. AGC unit 2336 is alsodesigned with gain contribution that is compensated in the final Up-linkSystem Link Gain G_(ul) calculations. Otherwise, the gain value of theAGC unit 2336 may be compensated in the Signal Conditioning unit 2340.If AGC unit 2336 is used in booster unit 2300 and the unit is designedfor Code Division Multiple Access (CDMA) cellular networks, AGC unitbandwidth is selected to be much smaller than the power controlrepetition rate of the CDMA system, for example less than 1.5 kHz inWCDMA networks, so that AGC operation does not interfere with theclosed-loop power control.

If the AGC unit 2336 is not included, the AD/C unit 2338 supplies asuitable dynamic range which can be as high as 192 dB (32-bits). TheAD/C unit 2338 is connected to Signal Conditioning unit 2340. The SignalConditioning unit 2340 performs such tasks as channel select filteringfor the selected operating frequency band, frequency conversion, signallevel estimation, AGC algorithm, and other signal conditioning andprocessing features. For example, the channel select filters that can beimplemented as poly-phased filters can be set for a given operatingbandwidth of 1.3, 5, 10 or 15 MHz, operating at any position within theforward-link cellular or Personal Communication Services (PCS) or otherselected frequency spectrum. Depending on system parameters such asoperational bandwidth and supported operation load such as filtering,the Signal Conditioning unit 2340 may be implemented by a variety oftechnologies such as Field-Programmable Gate Arrays (FPGAs),Application-Specific Integrated Circuits (ASICs), and general purposeDigital Signal Processors (DSPs) such as Texas InstrumentsTMS320C6416-7E3 processor. The Signal Conditioning unit 2340 includesappropriate interfaces and memory. The Signal Conditioning unit 2340 isconnected to Digital-to-Analogue Converter (DA/C) unit 2342. The DA/Cunit 2342 includes post filtering that is appropriate after digital toanalogue conversion. The DA/C unit 2342 is connected to the Frequencyconverter unit 2343, which up-converts the frequencies of the inputsignal to the selected portion of cellular or Personal CommunicationServices (PCS) band of frequencies. The frequency converter unit 2343includes filtering for correct operation of the transmitter chain. Theoperating frequency of the frequency converter unit 2343 is set bymicro-controller unit 2350. The frequency converter unit 2343 isconnected to the power amplifier unit 2344, which is connected to thedirectional coupler unit 2346. Directional coupler unit 2346 isconnected to the calibration signal generator and transmitter unit 2352and power splitter unit, hybrid combiner 2354. Power splitter unit,hybrid combiner 2354 is connected to the complex-weight unit 2356. Thecomplex-weight unit 2356 is connected to the duplex filters 2309 and2310 and the micro-controller 2350. The duplex filters 2310 and 2309 areconnected to antennas 2304 and 2306 and connected to the RF switch 2308.The micro-controller 2350 is connected to calibration signal generatorand transmitter units 2352, 2323 and to calibration signal receiverunits 2348 and 2305. A simple user interface unit 2351, which can be akeypad, simple dipswitch or other device, is connected tomicro-controller unit 2350. Units 2305, 2323, 2313, 2321, 2348, 2335,2343, 2352 and 2350 are either connected to local oscillator unit 2356or derive clock or reference frequencies via clock unit 2353 from thelocal oscillator 2356. The Signal Conditioning units 2318 and 2340 clockfrequencies are supplied by clock unit 2353.

Although many functional units of the Network 1002 and the User 2002units are not used in the back-to-back unit 2302, operation and thefunction of many of the units in the booster 2302 remain fundamentallythe same as those described for the Network unit 1002 and User unit2002. In the digital implementation of booster unit 2302, functionalblocks for calibration signal generator and transmitter unit 2352 andthe calibration receiver unit 2348 can be included in the SignalConditioning unit 2340 for the uplink, and in the Signal Conditioningunit 2318 for the downlink operation. The operation and description ofthe calibration signal generator and transmitter units 2352 and 2323,and the calibration signal receiver units 2348 and 2305, in thereverse-link and forward-link are fundamentally similar to thosedescribed for the Network unit 1002 and User unit 2002. Since theantenna units 2304, 2306, 2328 and 2330 are placed in close proximity,antenna isolation can be provided by highly directional antennas withincreased front-to-back radiation ratios.

For reverse-link operation of the booster 2302, signals received throughantenna units 2328 and 2330 may be re-transmitted through the antennaunits 2304 and 2306 at a higher signal power. The re-transmitted signalscan be received again through the antenna units 2330 and 2328 and aretermed an “Up-link Returned-Signal”. The signal return path may causeinstability in booster operation. In the digital implementation of thebooster unit 2302, magnitude of the returned signal, the Up-linkReturned-Signal, may be reduced through various signal-processingtechniques. The selection, configuration, and effectiveness ofsignal-processing techniques depend on system parameters and operatingconditions. Most known multiple-path mitigation algorithms can also beapplied for return signal reduction. However, due to the extremely smallpropagation delays between the antenna units 2304, 2306 and the antennaunits 2328, 2330, and the limited temporal resolution of the system,conventional multiple-path mitigation algorithms may at best bedifficult and expensive to practically implement, and often aredetrimental to system operation.

An example of a novel filtering technique that avoids system difficultyis disclosed herein in the “Novel Channel Filtering” section. The novelfiltering imposes a “deliberate” delay in the re-transmission of thereceived signal to separate the returned signal, called an Up-linkReturned-Signal, from the original incident signal at the outputterminators of antenna units 2328 and 2330. A delay of about 1 μsecensures time separation of the retransmitted signal from the originalreceived signal and enables mitigation of the re-transmitted signal. Thedelay can be introduced in the Signal Conditioning unit 2340 so long asa sufficient size digital data buffer is available. The ChannelFiltering operation can also be performed by the Signal Conditioningunit 2340 or can be performed by a separate ASIC or FPGA connected tothe AD/C unit 2338 and the Signal Conditioning unit 2340. Thecalibration signal can be used for channel estimation after convergenceof the complex-weight unit 2356 weights W₀ and W₁ so that amplitude andthe phase of the overall channel response including the return path canbe estimated to enable setting of the Channel Filter taps. Inclusion ofthe Channel Filter in the signal path also affects operation of antennadiversity. As the channel estimation is performed, antenna switchingoperations are synchronized to eliminate two of four possiblepropagation paths. Antenna switching selection is controlled bymicro-controller unit 2350 so that channel estimation can be performedfor two propagation paths and two sets of Channel Filter coefficientscan be determined for filtering operation. Therefore, relevant filtercoefficients can be selected and switched in synchrony and in harmonywith antenna selection operation. The Channel Filtering technique doesnot completely mitigate the returned signal but is rather used tosufficiently suppress the return signal so that some system gain ispossible for the signal boosting operation. The “deliberate delay” mayalso be used in conjunction with any other known signal-processingalgorithm to reduce coupling between the two antenna sets 2304, 2306 and2330, 2328. The forward-link of the booster unit 2302 may be modified ina similar manner to include the delay and channel filtering.

Other techniques, such as the use of vertical polarization for antennaunits 2304, 2306 and horizontal polarization for antennas 2328, 2330 canfurther improve the system performance. Similarly, system performancemay be improved by use of directional antennas as in conventionalbooster and repeater systems.

The unique unit 2302 identity code and optionally device location may betransmitted to the cellular network and used to locate a user in anindoor environment by generating heavily coded, protected, low bit-ratedata, which contains a long known preamble, the unique identity code,and optionally the longitude and the latitude of the unit 2302. Theinformation can be pulse-shaped for low spectral leakage andsuperimposed on the reverse-link signal of a selected channel by anappropriate modulation scheme within the unit 2302. The choice of themodulation scheme is based on the operating cellular system. Forexample, for Global System for Mobile Communications (GSM), which usesconstant envelope modulation such as Gaussian Minimum Shift Keying(GMSK), amplitude modulation with low modulation index can be used. ForCDMA systems with fast reverse-link power control, Differential BinaryPhase Shift Keying (DBPSK) can be used as the modulation scheme.Information extraction from the received channel signal at base stationmay be performed through base station receiver modifications which donot affect normal operation of the cellular link.

An example of system operational flow diagrams for the booster unitshown in FIGS. 11 or 12 is shown in FIGS. 17A, 17B. The example does notinclude all the possible functionalities for complete operation ofbooster unit 2302 or 2252. The example may be considered to show aminimal control flow for most basic operations of the booster unit 2302or 2252. On “power-up”, “reset”, or a “Stop” instruction, booster unit2302 or 2252 sets complex-weight units 2360 and 2356 weights W₀ and W₁to an “Initial” value by default. The “Initial” weights values enableminimum power radiation from the two connected antennas with no phasedifferential between the two radiated fields, for example broadsideradiation. On “power-up” or “reset” instruction of the booster unit 2302or 2252, the micro-controller unit 2350 starts 2402 the control-flow inFIG. 17A. Micro-controller 2350 instructs the reverse-link calibrationreceiver 2348 to scan 2404 for all possible code offsets. If asubstantial signal power is transmitted by other units operating withinthe same geographical area is detected 2406 by the receiver unit 2348,the received signal powers are stored 2408. If no substantial signal isdetected 2410, the micro-controller 2350 instructs the forward-linkcalibration receiver 2305 to scan 2410 for all possible code offsets. Ifa substantial signal power is transmitted by other units operatingwithin the same geographical area and detected 2416 by the receiver unit2305, the received signal powers are stored 2414. After the test for allpossible code offsets is finished for the forward and reverse links ofthe system and if other units signal power is detected 2417, thereceived signals for each offset are tested and the largest signal poweris selected 2412. If the selected signal power is above a safe threshold2418, the unit 2302 displays 2419 an error message and stops operation2422. If the selected signal power is below the safe threshold, the unitproceeds to action 2420. If no substantial signal is detected or thedetected signals are below the safe threshold 2416, the micro-controller2350 selects 2420 an unused code offset for both forward and reversechannel-sounding transmissions. Micro-controller 2350 sets 2424 thebooster unit 2302 or 2252 in “channel-sounding” mode. In“channel-sounding” mode, diversity switches 2308 and 2326 are maintainedin the current position and not switched. Micro-controller 2350 sets2426 the complex-weight units 2356 and 2360 weights W₀ and W₁ to the“Initial” value. Micro-controller 2350 instructs calibration signalgenerator and transmitter units 2352 and 2323 to commence transmission2428 with the specified “own code” phase continuously. Themicro-controller 2350 also instructs the up-link calibration signalreceiver unit 2348 to attempt to receive 2430 the channel-soundingsignal for the code offset used by the transmitter unit 2352. If nosubstantial channel-sounding signal is detected with the specified setof weights of the complex-weight unit 2356 and Up-link System Link GainG_(ul) is less than the specified maximum allowed system gain 2434,micro-controller 2350 modifies and issues 2436 new up-link weight valuesto complex-weight unit 2356 such that transmit power of thechannel-sounding signal from antenna units 2304 and 2306 is increased bya predetermined step size dG while maintaining relative phases ofweights W₀ and W₁. Actions 2430, 2432, 2434 and 2436 are repeated untila substantial channel-sounding signal is detected for uplink path or themaximum allowed up-link system gain is reached. If maximum allowedup-link system gain is reached, the most recent weights are maintainedunchanged 2438 as the most optimum weights for normal operation. Ifmaximum allowed system gain is not reached and no substantialchannel-sounding signal exists at the output of the calibration signalreceiver 2348, an adaptive convergence algorithm such as Least-MeansSquared (LMS) is used to further modify weights W₀ and W₁ such that thechannel-sounding signal power is minimized 2442. The new weights areissued to the complex-weight unit 2356 for transmission of thechannel-sounding signal 2444. If the up-link weights are sufficientlyconverged, control-flow proceeds, otherwise actions 2430 to 2446 arerepeated. After the successful convergence of the up-link weights W₀ andW₁, micro-controller 2350 converges the down-link weights in actions2448 to 2460 in much the same way as the up-link weights. Aftersuccessful convergence of both up-link and down-link weights,micro-controller 2350 exits 2462 the channel-sounding mode.Micro-controller 2350 instructs the calibration signal receivers 2348and 2305 to continue 2464 to receive the channel-sounding signaltransmitted by the calibration signal transmitter units 2352 and 2323.If the safe average channel-sounding signal power level is exceeded fora substantial amount of time 2468 for the up-link or down-link path, themicro-controller 2350 sets 2470 both up-link and down-link weights to“Initial” value and returns 2474 to action 2402. If the averagechannel-sounding signal power level is within the expected range, thecalibration signal receiver units 2348 and 2305 are instructed toreceive and detect 2469 channel-sounding signals with all other possiblecode offsets. If no channel-sounding signal with substantial averagesignal power level is detected in the up-link or down-link, themicro-controller 2350 returns 2472 to action 2464. The channel-soundingoperation can be initiated on regular bases to ensure correct operationbefore detection of excess signal in either the up-link or down-link ofthe booster 2302, 2252 paths.

Channel Filtering Example

The example can be applied to the booster system to counter the effectof the feed-back loop and the Up-link Returned-Signal that may exist inthe reverse-link of the system and Down-link Returned-Signal that mayexist in the forward-link of the system. “Channel Filtering” for theforward and the reverse links is autonomous and can either be applied toboth or one of the forward or the reverse links of the system, and canbe implemented in the Network unit 1002, the User unit 2002, or both. Asimplified block diagram of the booster with channel filteringcapability in isolation is shown in FIG. 17. Reverse-link operationalone is discussed for the Network unit 1002 and User unit 2002. ChannelFiltering is applicable to all digital implementations. In therepresentation, no antenna diversity is assumed for either the Networkunit 2452, which is substantially similar to 1002 in FIG. 9, or the Userunit 2454, which is substantially similar to 2002 in FIG. 10. Theprocessing and propagation delays within the booster system can becategorized as the following:

τ_(Us)=the User unit 2454 processing delay (relatively negligible).

τ_(P1)=the unlicensed band propagation delay.

τ_(Nrx)=the Network unit 2452 receiver processing delay (relativelynegligible).

τ_(Ntx)=the Network unit 2452 transmitter processing delay (relativelynegligible).

τ_(d)=the “deliberate” delay introduced in the transmission path of theNetwork unit 2452.

τ_(P2)=the licensed band propagation delay of the Up-linkReturned-Signal.

The overall impulse response 2464 of the booster unit 2451 is shown. Theoriginal incident pulse enters from antenna 2462 (A1) and arrives at theinput terminal of the Network unit 2452 receiver after a delay of τ_(f,)with the pulse 2468 shown where:

τ_(f)=τ_(Us+)τ_(P1≈)τ_(P1)

The pulse is amplified and transmitted 2470 after the “deliberate” timedelay τ_(d,) from antenna 2456 (marked A4 in FIG. 17). The transmittedsignal re-enters the antenna 2462 (A1) after the propagation delayτ_(P2) and arrives at the input to the Network unit 2452 receiver aftera delay 2472 of τ_(f). The overall delay for the Up-link Returned-Signalat the input to the Network unit 2452 receiver is τ_(t) and issubstantially equal to:

τ_(t)=τ_(Nrx+)τ_(d+)τ_(Ntx+)τ_(P2+)τ_(f≈)τ_(d+)τ_(P1+)τ_(P2)

The returned pulse 2472 is delayed by the propagation path delays τ_(P1)and τ_(P2), which can be very small in the booster's operatingenvironment. The “deliberate” delay is introduced to sufficientlyseparate the Up-link Returned-Signal from the original incident pulse,such that filter coefficients can be estimated easily and filtering canbe performed more effectively. Introduction of another “deliberate”delay in the transmit path of the User unit 2454 ensures separation ofthe boosted transmitted pulse and the Up-link Returned-Signal, acondition that may be desirable to reduce the effect of the multipathexperienced by the boosted transmitted pulse on the operation of theChannel filtering.

In the example, “Channel Filtering” unit 2512 shown in FIG. 18 is placedonly on the reverse-link of the Network unit 1002. The channel filteringprocess involves estimating the complex propagation channel impulseresponse including amplitude and phase for all time delays up to themaximum expected multipath delay. The complex channel impulse responseC(t,τ) can be provided by the calibration signal receiver unit 1016shown in FIG. 9 because the information is readily available at theoutput of the unit for the reverse-link path of the system. Based on thedescribed design of the calibration signal technique shown in FIGS. 13A,13B, and 13C, the channel impulse response provided by the calibrationsignal receiver unit 1016 does not include the delay contributions ofthe “deliberate” delay (τ_(d)) and the τ_(Nrx+)τ_(Ntx) components. Whileτ_(Nrx+)τ_(Ntx) is sufficiently small to ignore, the “deliberate” delay(τ_(d)) is added in the overall impulse response in the Network unit1002 for the estimation of the Channel Filter coefficients. Similarly,if Channel Filtering operation is also used for the forward-link, aseparate complex channel impulse response is used for the link. As aresult, a similar calibration technique to the reverse-link is performedon the forward-link. An example of the estimated power of the channelimpulse response C(t,τ) 2510 at the output of the calibration signalreceiver 1016 is shown in FIGS. 15A. 15B, and 15C. The impulse response2510 is for a maximum delay of 1 μsec assuming a calibration signal PNcode chipping rate of 5 Mchips/sec and 2 samples per chip. In FIG. 15A,C(t,τ) 2510 has three substantial distinguishable propagation paths atdelays of 0.2 (P1), 0.4 (P2) and 1.0 (P3) μsec respectively. The maximumexpected time delay corresponds to a signal path of about 300 meterswhich is reasonable for the booster range and operational environment.The 1.0 μsec maximum time delay in combination with a “deliberate delayτ_(d) of 1 μsec may be implemented using a 21-tap complex finite impulseresponse (FIR) filter with half-chip tap spacing for Channel Filteringoperation.

FIG. 15A shows the Channel Filter unit 2512. The Channel Filter unit2512 has a 21-tap FIR filter 2506 with tap delay of D=0.1 μsec spacingand with variable complex coefficients set to the values shown in table2508. The FIR filter 2506 output is connected to one of the inputs ofthe adder unit 2504 and the input of the FIR filter unit 2506 isconnected to the output of the adder unit 2504. The other input of theadder unit 2504 is connected to the AD/C 2502. In the example, the AD/Cis the unit 1046 in FIG. 9. The FIR filter 2506 produces a replica ofthe received signal at the selected time delay with the respectivecomplex coefficient specifying the magnitudes and the phases of thereceived Up-link Returned-Signal to “wipe off” the incoming first (P1),second (P2) and third (P3) return signal components. The FIR filter 2506can either be implemented by a Field-Programmable Gate Array (FPGA),Application-Specific Integrated Circuit (ASIC) or by the SignalConditioning unit 1048 in FIG. 9. The processes of channel estimationC(t,τ) and up-dating the FIR filter 2506 filter coefficients areperformed continuously with an update rate that depends on the channelcoherence time. For the example, a value of 100 msec can be assumed asthe indoor channels exhibit large coherence time. Other embodiments mayinclude an adaptive algorithm such as Normalized Least Mean-Square(NLMS) and Recursive Least Squares (RLS), which converge on the receivedcalibration signal at the Network unit 1002 to estimate the filtercoefficients on an on-going basis.

Wire Connected Booster

FIG. 17 shows an example of analogue implementation of the Network unit600 using a transmission cable as the physical medium for communicationwith the User unit 4000 shown as unit 702 in FIG. 6. The Network unit602 shown in FIG. 5 is modified to the form of unit 3005 shown in FIG.16 to transmit and receive signals from the User unit 4005 over a cableconfigured to support the operating bandwidth and the frequencies of theNetwork unit 3005 and User unit 4005 signals. The User unit 4005 shownin FIG. 17 is a modified version of the User unit 702 shown in FIG. 6.The cable interface unit 3020 comprises a line interface unit 3160 whichis connected to the transmission/reception cable 3170 and hybridcombiners 3140 on the forward-link and 3150 on the reverse link of theNetwork sub unit 3010. The line interface unit 3160 performs loadmatching for connection to a transmission line 3170 and includes otherappropriate components such as the amplifiers, modulation and frequencyconverters with modem functionality for reliable transmission over thetransmission line 3170. Design of the line interface unit 3160 isdependent on the transmission line 3170 characteristics. For example,in-building power lines or telephone lines can be used as a transmissionline 3170 as in homePNA and HomeNetworking, where the line interfaceunit 3160 is designed for such transmission. The hybrid combiner ordirectional coupler 3140 may be used to combine the control link 3110signal with the forward-link signal. Otherwise, output lines from thedirectional coupler unit 3040 and the control link unit 3110 can beconnected directly to line interface unit 3160, where signals aremodulated on adjacent carriers for simultaneous transmission to the Userunit 4005. The hybrid combiner or directional coupler 3150 is used toextract sufficient signal for reception and detection of control link3110 received signal. In another embodiment, the input lines to thedirectional coupler unit 3130 and the control link unit 3110 candirectly be connected to line interface unit 3160 if the control anddata signals are modulated on adjacent carriers for simultaneoustransmission from the User unit 4005. Hybrid combiners may be usedinstead of the directional couplers 3040, 3130 and 3085. Reverse-linkNetwork unit 3060 receiver internal LNA amplifier may be positionedbefore the directional coupler 3130 or the hybrid combiner replacement,in FIG. 16.

Operation of the units 3015, 3030, 3050, 3120, 3110, 3060, 3100, 3105,3070, 3074, 3078, 3080, 3085, 3040, 3130, 3072, 3092, 3094, and 3090 inFIG. 16 is similar to that of units 640, 624, 604, 620, 628, 606, 626,627, 614, 610, 608, 612, 618, 630, 616, 613, 646, 648, and 622respectively, as discussed in the description of FIG. 5. In the modifiedNetwork unit 3005, the directional coupler 3040 (630 in FIG. 5) isconnected to hybrid combiner 3140, and the directional coupler 3130 (616in FIG. 5) is connected to hybrid combiner 3150.

FIG. 16 shows an example of analogue implementation of the User unit 702(FIG. 6) using a transmission cable as the physical medium forcommunication with the Network unit 3005 (602 in FIG. 5). The User unit702 shown in FIG. 6 is modified into the form of unit 4005 shown in FIG.17 to transmit and receive signals from the Network unit 3005 over acable capable of supporting the operating bandwidth and the frequenciesof the Network 3005 and User 4005 units' signals. Network unit 3005 is amodified version of the Network unit 602 shown in FIG. 5. Cableinterface unit 4020 comprises a line interface unit 4150 which isconnected to the transmission/reception cable 4160 and two hybridcombiners 4130 on the forward-link and 4140 on the reverse link of theUser sub unit 4010. The line interface unit 4150 performs load matchingfor connection to a transmission line 4160. Other suitable componentssuch as the amplifiers, modulation and frequency converters with modemfunctionalities may be used to enable reliable transmission over thetransmission line 4160. Design of the line interface unit 4150 isdependent on the transmission line 4160 characteristics. For example,even in-building power lines or telephone lines can be used as thetransmission line 4160 as in homePNA and HomeNetworking applicationswhere the line interface unit 4150 is designed for such operation. Thehybrid combiner, mixer, or directional coupler 4140 is used to combinethe control link 4120 signal with the reverse-link signal. The hybridcombiner or duplexer 4130 is used to extract sufficient signal forreception and detection of control link 4120 received signal. Hybridcombiners may also be used instead of the directional coupler 4110. Insome embodiments, the Forward-link Network unit 4080 internal LNAamplifier may be positioned before the directional coupler 4110 or thehybrid combiner replacement, shown in FIG. 17.

Operation of the units 4015, 4030, 4040, 4050, 4070, 4075, 4080, 4090,4100, 4110, 4060, 4062, 4152, 4154, 4128, 4126, 4124, 4122, and 4120 inFIG. 17 is similar to that of units 722, 734, 736, 732, 728, 721, 724,726, 716, 718, 754, 756, 745, 748, 746, 744, 742, 740, and 720respectively, as discussed with respect to FIG. 6. In the modified Userunit 4005, the directional coupler 4110 (718 in FIG. 6) is connected tohybrid combiner 4130, and the Reverse-link User unit 4090 (726 in FIG.6) is connected to hybrid combiner 4140.

Operation of Network unit 3010 is similar to the operation of theNetwork unit 602 and the operation of User unit 4010 is similar to theoperation of the User unit 702.

The control-flow description given for FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C,and 8D can also be used for the digital implementation of the Networkunit 3005 and User unit 4005, described with reference to FIGS. 16 and17.

FIG. 18 shows an example of digital implementation of the Network unit5005 (1002 in FIG. 9), which uses a transmission cable as a physicalmedium for communication with the User unit 6005 (2002 in FIG. 10). TheNetwork unit 1002 shown in FIG. 9 is modified to the unit 5005 shown inFIG. 18 to transmit and receive signals from the User unit 6005 shown inFIG. 19 over a cable capable of supporting the operating bandwidth andthe frequencies of the Network 5005 and User 6005 unit signals. Userunit 6005 is a modified version of the User unit 2002 shown in FIG. 10.Modified cable interface unit 5020 comprises a line interface unit 5220,which is connected to the transmission/reception cable 5210 and the LineModem unit 5250.

The line interface unit 5220 and the Line Modem unit 5250 perform loadmatching for connection to transmission line 5210. Other suitablecomponents may be included such as amplifiers, and modulation andfrequency converters to enable reliable transmission over thetransmission line 5210. The design of the line interface unit 5220 isdependent on the transmission line 5210 characteristics. For example,even the in-building power lines or telephone lines can be used as thetransmission line 5210 as in a homePNA application, where the lineinterface unit 5220 is designed for such operation. The line modem unit5250 may be used for modulation and demodulation AD/C, DA/C and allother modem functionalities for transmission of the signal generated bythe unit 5010 and reception of signal generated by unit 6010. Also,design of the modem unit 5250 may implement example technologies such ashomePNA and Home Networking. Line modem unit 5250 is connected to datamultiplexer unit 5260 and data demultiplexer unit 5270. The line modemunit 5250 can be implemented in analogue, digital, or hybrid technology.In the illustrative example, line modem unit 5250 is implemented indigital domain.

Data multiplexer unit 5260 is also connected to Signal Conditioning unit5110 and the control link unit 5145, and is used to multiplex controlsamples generated by control link unit 5145 and the signal samplesgenerated by the Signal Conditioning unit 5110. The multiplexer unit5260 can be integrated within the Signal Conditioning unit 5110.Otherwise, output lines of the Signal Conditioning unit 5110 and controllink unit 5140 can be separately connected to the line modem unit 5250and modulated on adjacent carriers for simultaneous transmission to theUser unit 6005.

Data Demultiplexer unit 5270 is also connected to Signal Conditioningunit 5130 and the control link unit 5145 and is used to demultiplexreceived control samples and the signal samples generated by the Userunit 6005. The demultiplexer unit 5270 can be integrated within theSignal Conditioning unit 5130. Otherwise, the input line to the SignalConditioning unit 5130 and control link unit 5145 can be separatelyconnected to the line modem unit 5250 if the control and data signalsare modulated on adjacent carriers for simultaneous transmission by theUser unit 6005.

In Network unit 5005, the calibration signal receiver unit (1016 in FIG.9) is no longer implemented separately. No analogue signal path isavailable in the reverse-link of the Network unit 5005, so thecalibration signal receiver unit (1016 in FIG. 9) is integrated andoperates in the Signal Conditioning unit 5130.

Operation of the units 5110, 5120, 5130, 5140, 5141, 5145, 5386, 5100,5150, 5090, 5160, 5080, 5170, 5070, 5180, 5190, 5060, 5050, 5040, 5082,5060, 5064, and 5030 in FIG. 18 is similar to that of units 1022, 1024,1048, 1060, 1061, 1062, 1070, 1020, 1050, 1018, 1052, 1014, 1054, 1012,1056, 1058, 1010, 1008, 1004, 1007, 1010, 1072, and 1006 respectively,as discussed for FIG. 9.

FIG. 19 shows an example of digital implementation of the User unit 6005(2002 in FIG. 10) using a transmission cable as the physical medium forcommunication with the Network unit 5005 (1002 in FIG. 9). The User unit2002 shown in FIG. 10 is modified to the form of unit 6005, shown inFIG. 19 to transmit and receive signals from the Network unit 5005,which is a modified version of the Network unit 1002 shown in FIG. 9over a cable capable of supporting the operating bandwidth and thefrequencies of the Network 5005 and User 6005 units signals. Themodified cable interface unit 6020 comprises a line interface unit 6230which is connected to the transmission/reception cable 6240 and the linemodem unit 6220.

The line interface unit 6230 an d the Line Modem unit 6220 perform loadmatching for connection to transmission line 6240. Other suitablecomponents such as the amplifiers, modulation and frequency convertersmay be included for reliable transmission over the transmission line6240. Design of the line interface unit 6230 is dependent on thetransmission line 6240 characteristics. For example, even in-buildingpower lines or telephone lines can be used as the transmission line 6240as in homePNA operation where the line interface unit 6230 is designedaccordingly. The line modem unit 6220 may be used for modulation anddemodulation, AD/C, DA/C and other functionalities for transmission ofthe signal generated by the unit 6010 and reception of signal generatedby unit 5005. Design of the modem unit 6220 may be implemented invarious example technologies such as homePNA and Home Networking. Linemodem unit 6220 is connected to data multiplexer unit 6200 and datademultiplexer unit 6210. The line modem unit 6220 can be implemented inanalogue, digital, or hybrid technology. In the illustrative exampleline modem unit 6220 is assumed to be implemented in digital domain.

Data multiplexer unit 6210 is also connected to Signal Conditioning unit6140 and the control link unit 6150 and is used to multiplex controlsamples generated by control link unit 6150 and the signal samplesgenerated by the Signal Conditioning unit 6140. The multiplexer unit6210 can be integrated within the Signal Conditioning unit 6140.Otherwise, the output lines of the Signal Conditioning unit 6140 andcontrol link unit 6150 can be separately connected to the line modemunit 6220 and modulated on adjacent carriers for simultaneoustransmission to the Network unit 5005.

Data Demultiplexer unit 6200 is also connected to Signal Conditioningunit 6100 and the control link unit 6150 and may be used to demultiplexreceived control samples and the signal samples generated by the Networkunit 5005. The demultiplexer unit 6200 can be integrated within theSignal Conditioning unit 6100. Otherwise, the input to the SignalConditioning unit 6100 and control link unit 6150 can be separatelyconnected to the line modem unit 6220 if the control and data signalsare modulated on adjacent carriers for simultaneous transmission by theNetwork unit 5005.

Operation of units 6150, 6100, 6110, 6140, 6155, 6151, 6120, 6130, 6090,6160, 6170, 6080, 6180, 6070, 6190, 6060, 6050, 6030, 6062, 6064, 6066,6068, 6072, and 6040 in FIG. 19 is similar to that of units 2056, 2020,2022, 2046, 2054, 2055, 2021, 2023, 2024, 2044, 2042, 2026, 2040, 2028,2038, 2030, 2032, 2034, 2031, 2072, 2070, 2027, 2025, and 2036respectively, as discussed in the description of FIG. 10.

The control-flow description given for FIGS. 7A, 7B, 7C, 7D, 8A, 8B, 8C,and 8D can also be used for the digital implementation of the Networkunit 5005 and User unit 6005, which is discussed above in FIGS. 18 and19.

Operation of Network unit 5010 is similar to the operation of theNetwork unit 1002 and the operation of User unit 6010 is similar to theoperation of the User unit 2002.

Channel Estimation by Matrix Inversion

Most digital communication systems use a type of channel estimation.Channel estimation is usually based on a known transmitted sequenceknown as a “preamble” or “midamble” or “training sequence” among othernames. The known sequence is used for channel estimation as variousalgorithms use the priori knowledge to estimate the propagation channelcomplex parameters and characteristics. Two basic signal processingdomains are fundamentally used for channel estimation including (1) atime domain approach, and (2) a frequency domain approach. The timedomain approach includes many algorithms, most notably“correlation-based” and “Matrix inversion” algorithms. While correlationbased channel estimation are frequently used, mainly due to simplicityand low computation demands, matrix inversion channel estimation yieldsbetter performance at a higher computation cost. “Matrix inversion”channel estimation algorithms may otherwise be used.

The complex impulse response coefficients of a propagation channel oflength n may be estimated using a single transmitted sequence that isusing a known PN code of length s samples, where s>n. The time invariantchannel coefficients may be represented by matrix H given as:

H^(T)=[h₁ h₂ . . . h_(n)]

and the transmitted PN sequence as M given by:

M^(T)=[m₁ m₂ . . . m_(s)]

All s samples of the code are not needed for the channel soundingoperation. The convolution between the Channel coefficients and thetransmitted sequence yields the received signal e_(t) given by:

e₁ = m_(n) ⋅ h₁ + … + m₂ ⋅ h_(n − 1) + m₁ ⋅ h_(n)e₂ = m_(n + 1) ⋅ h₁ + … + m₃ ⋅ h_(n − 1) + m₂ ⋅ h_(n) ⋮ ⋮ ⋮e_(k) = m_(k + n) ⋅ h₁ + … + m_(k + 1) ⋅ h_(n − 1) + m_(k) ⋅ h_(n)

where t denotes time and k is the maximum required estimation length,and a relationship s>k+n is assumed.

The above set of equations, representing e_(t), can be shown in matrixnotation as the following:

E=V.H

where the received complex samples, E, can be represented as:

E^(T) = [e₁e₂  …  e_(k)] and: $V = \begin{matrix}m_{n} & m_{n - 1} & \ldots & m_{1} \\m_{n + 1} & m_{n} & \ldots & m_{2} \\\vdots & \; & \; & \; \\\vdots & \; & \; & \; \\m_{k + n} & m_{k + n - 1} & \ldots & m_{k}\end{matrix}$

The complex channel impulse response can be calculated by matrixinversion of V matrix as shown below:

I.H=V¹.E

where I is an Identity matrix with dimensions of n×n. If k=n, uniquevalues of the channel impulse response can be calculated using the abovematrix inversion approach. V matrix can be pre-calculated and stored inmemory, so that high computation complexity is avoided.

1-44. (canceled)
 45. A method for mediating wireless communications between a network transceiver and a user transceiver in a wireless communication system, the method comprising: generating a two-way communication pathway between a network unit and a user unit to facilitate signal communication between the network transceiver and the user transceiver in separate repeater hops between the network transceiver and the network unit, between the user transceiver and the user unit, and between the network unit and the user unit; and communicating signals to each of the network unit and the user unit in an operating frequency band of the network transceiver or user transceiver respectively such that radio frequency isolation between the network unit and the user unit is maximized, and the signal communication between the network unit and the user unit has a signal waveform that is independent of the operating frequency band of the signal communication between the network and user transceivers.
 46. The method in accordance with claim 45, wherein communicating signals to each of the network unit and the user unit includes beam-forming the signals to each of the network unit and the user unit.
 47. The method in accordance with claim 45, wherein communicating the signals to each of the network unit and the user unit includes controlling an effective radiated power to increase coverage area of the riser unit.
 48. The method in accordance with claim 45, wherein communicating signals to each of the network unit and the user unit includes controlling an effective radiated power to improve link quality of the network unit.
 49. The method in accordance with claim 45, wherein communicating signals to each of the network unit and the user unit includes using transmit antennas at the network and user transceiver operating frequency, and using beam-formers to control an effective radiated power of the network unit and user unit to increase coverage area of the user unit.
 50. The method in accordance with claim 45, wherein communicating signals to each of the network unit and the user unit includes using receiver antennas at the network and user transceiver operating frequency, and using beam-formers to control antenna radiation patterns of the network unit and user unit to increase coverage area of the user unit.
 51. The method in accordance with claim 45, wherein the repeater hop between the network unit and the user unit is tuned to operate at a frequency band selected from a group consisting of an Unlicensed National Information Infrastructure (U-ISM) spectrum frequency band, an Unlicensed Personal Communication Services (U-PCS) spectrum frequency band, an Industrial, Scientific and Medical (ISM) spectrum frequency band, and any unlicensed frequency band.
 52. The method in accordance with claim 45, further comprising compensating for propagation losses between the network unit and user unit alone using a gain controller.
 53. The method in accordance with claim 45, wherein the repeater hop between the network unit and the user unit on the communication pathway communicates on a carrier signal that is independent of signals communicated between the repeater and the network and user transceivers.
 54. The method in accordance with claim 45, wherein the repeater hop between the network unit and the user unit on the communication pathway communicates at a carrier frequency that is independent of signals communicated between the repeater and the network and user transceivers.
 55. The method in accordance with claim 45, wherein the repeater hop between the network unit and the user unit on the communication pathway communicates with a signal waveform that is independent of signal waveform communicated between the repeater and the network and user transceivers.
 56. The method in accordance with claim 45, wherein dedicated wireless data and/or control links in the communication pathway between the network unit and the user unit operate at unlicensed frequency bands.
 57. The method in accordance with claim 45, wherein dedicated wireless data and/or control links in the communication pathway between the network unit and the user unit operate according to a wireless standard.
 58. The method in accordance with claim 45, wherein dedicated wireless data and/or control links in the communication pathway between the network unit and the user unit are power-controlled for operation at reduced transmit power.
 59. The method in accordance with claim 45, wherein the network unit and/or the user unit comprise: a pair of antennas; and a switch connected to the pair of antennas that performs switching operations for transmit/receive operations enabling switched antenna diversity in all or some of the separate repeater hops.
 60. A method for mediating wireless communications between a network transceiver and a user transceiver in a wireless communication system, the method comprising: establishing a network link with the network transceiver; establishing a user link with the user transceiver; generating a two-way communication pathway between a network unit and a user unit to facilitate signal communication between the network transceiver and the user transceiver in separate repeater hops between the network transceiver and the network unit, between the user transceiver and the user unit, and between the network unit and the user unit; and communicating signals to each of the network unit and the user unit in an operating frequency band of the network transceiver or user transceiver respectively such that radio frequency isolation between the network unit and the user unit is maximized, the signal communication on the network link and the user link having a signal waveform that is independent of the operating frequency band of the signal communication between the network and user transceivers.
 61. The method in accordance with claim 60, wherein the repeater hop between the network unit and the user unit is tuned to operate at a frequency band selected from a group consisting of an Unlicensed National Information Infrastructure (U-ISM) spectrum frequency band, an Unlicensed Personal Communication Services (U-PCS) spectrum frequency band, an Industrial, Scientific and Medical (ISM) spectrum frequency band, and any unlicensed frequency band.
 62. The method in accordance with claim 60, wherein the repeater hop between the network unit and the user unit on the communication pathway communicates with a signal waveform that is independent of signal waveform communicated between the repeater and the network and user transceivers.
 63. A repeater that mediates communication between a network transceiver and a user transceiver in a wireless communication system, the repeater comprising: a network unit that communicates with the network transceiver; a user unit that communicates with the user transceiver; a two-way communication pathway between the network unit and the user unit to facilitate signal communication between the network transceiver and the user transceiver in separate repeater hops between the network transceiver and the network unit, between the user transceiver and the user unit, and between the network unit and the user unit; and a signal processing unit respectively coupled to the network unit and the user unit, each signal processing unit to communicate signals in an operating frequency band of the network and user transceivers, and to control effective radiated power of the signals; the communication between the network unit and the user unit having a signal waveform that is independent of the operating frequency band of the communication between the network and user transceivers.
 64. The repeater in accordance with claim 19, wherein the signal processing unit is a beam-former unit. 